It is still missing a lot, but in the process of developing Balanced Brawl, I found a bunch of previously undocumented action IDs. Anyone wanting to do frame speed or conditional modification should find this handy. Feel free to use this on any of your own projects; I consider this, as research, to be properly free information.
Do note that this is based off the list in one of the old sticky topics, just updated. I noted what I added not out of egoism but so you know the difference in sources (that is, my guess versus other guesses). If anyone has any other documented action IDs, I'll happily add them. Do note that a lot of my unknown action IDs with very poor descriptions are probably aerial actions... I didn't do nearly as much testing in the air as I did on the ground.
000 Stand
001 Walk
002
003 Start Dash
004 Run
005 Stop
006 Turn 1
007 Turn 2
008 Stop Turn
009
00A Start Jump
00B Jump
00C Second Jump
00E Fall 1
00F Fall 2
010 Fall Dissabled
011 Enter Crouch
012 Crouch
013 Crawl Forwards
014 Crawl Backwards
015 Exit Crouch
016 Land 1
017 Land 2
018 arial-atk lag
019 Land Dissabled
01A Enter Shield
01B Shield
01C Exit Shield
01D shield stun
01E Dodge (AA note: is actually the Spotdodge)
01F Roll Forward
020 Roll Back
021 Air Dodge
022 Spotdodge (AA addition, broken)
023 Spotdodge (AA addition, broken)
024 N Attack(and Combo)
025 Rapid jab? (AA addition)
026 R Attack
027 S Attack
028 U Attack
029 D Attack
Eternal Yoshi clarification:
02A Side Smash Windup
02B Side Smash Charge
02C Side Smash Attack
02D Down Smash Windup
02E Down Smash Charge
02F Down Smash Attack
030 Up Smash Windup
031 Up Smash Charge
032 Up Smash Attack
033 Air Attack(All)
034 Grab
035 Grabbing Enemy
036 Dash Grab (AA addition)
037 Holding Enemy (AA addition)
038 Pivot Grab (AA addition)
039 Hold
03A Grab Attack
03B Release
03C Throw
03D Grabed
03E Held
03F Held Damage
040 Escape
041 jump break (AA added)
042 Thrown
043 odd slightly duck downward (AA added) ???
044 odd landing animation (AA added) ???
045 Hitstun
046 Hit ground
047 Hit wall
048 Hit ceiling
049 Tumble
04A Hit ground (tumble)
04B Hit wall (tumble)
04C Hit ceiling (tumble)
04D Lying
04E tech roll from lying on ground (AA added)
04F struggle on ground a bit (AA added)
050 tech roll from lying on ground (AA added)
051 get up
052 tech roll from lying on ground (AA added)
053 get up attack (AA added)
054 bounce on ground (AA added, speed up to remove jab locks)
055 hit ground hard (AA added)
056 broken shield that flies up (AA added)
057 hit ground hard with broken shield (AA added)
058 hit ground softly with broken shield (AA added)
059 get up from lying on ground with broken shield (AA added)
05A shield broken dizziness (AA added)
05B recover from broken shield (AA added)
05C fall asleep (AA added)
05D something in the middle of sleep (AA added)
05E wake up from sleep (AA added)
05F stunned from Deku Nut (AA added, mistaken for Mewtwo's Disable state haha)
060 tech (gound)
061 tech roll
062 tech (wall)
063 tech jump
064 tech (ceiling)
065 run into a wall (AA added)
066 strange compress thing (AA added) ???
067 footstool the enemy (AA added)
068 face the screen (AA added, can still do moves toward screen, WAY too cool) ???
069 odd really quick landing effect (AA added) ???
06A t-pose's Toon Link briefly then landing effect (AA added) ???
06B Mr. Game & Watch tpose's briefly and is then all black, no outline (AA added) ???
06C t-pose's Meta Knight briefly and then landing effect with eye glimmer (AA added) ???
06D quick jerk and then landing effect (AA added) ???
06E get footstooled on ground (AA added)
06F brief odd thing (AA added) ??? [helpless fall state in air]
070 get footstooled in air (AA added)
071 flop down hard on ground (AA added) ??? [spinning helpless after being footstooled in air?]
072 soft landing effect (AA added) ??? [falls really fast in air]
073 begin to grab ledge (AA added) [if forced in air, puts you in fall1 state with aerial jumps restored]
074 ledge grab
075 ledge hange
076 soft landing effect, probably some ledge action (AA added) ???
077 on ground for one frame, probably a ledge action (AA added) ???
078 soft landing effect, probably a ledge action (AA added) ???
079 ledge jump
07A ledge jump, perhaps 100% plus (AA added)
07B interesting pose for 1 frame, probably a ledge action (AA added) ???
07C begins to teeter off a ledge (AA added)
07D teetering off a ledge (AA added)
07E lands on ground hard (AA added) ???
07F freezes the game when Meta Knight tries it (AA added) ???
080 some sort of landing effect (AA added) ???
081 t-pose -> center of stage -> on rear end for a moment (Subspace teleport?) (AA added) ???
082 freezes the game when Meta Knight tries it (AA added) ???
083 big smoke cloud landing effect (AA added) ???
084 flop on ground and land on stomach (AA added) ???
085 freezes the game when Toon Link/Mr. Game & Watch does it (AA added) ???
086 get up from lying on stomach (AA added)
087 Toon Link t-pose's and then lands on the ground softly, Meta Knight makes it look like it's related to gliding (AA added) ???
088 Toon Link t-pose's and then lands on the ground softly, related to gliding (AA added) ???
089 trip on rear end, running over banana peel activates this (AA added)
08A related to tripping on rear end, getting hit by Diddy Kong's banana peels inflicts this (AA added)
08B turn around and trip (AA added)
08C fall forward and trip (AA added)
08D on the ground in a tripped state (AA added)
08E get up from tripped state (AA added)
08F attack from tripped state (AA added)
090 roll forward out of tripped state (AA added)
091 roll backward out of tripped state (AA added)
092 climb ladder
B4/B5: surfacing animation (same?)
B6: treading water (good health)
B7/B8: actively swimming (as in swimming forward) [no evidence B8 is used]
B9/BA: turning around in water [no evidence BA is used]
BB: floundering (about to drown)
BC: drowning
C7: Enter grounded state
C8: In grounded state
C9: Exit grounded state
CA: Frozen state
CB: Exiting frozen state
0BD Death
*0BE Respawn
EC: In Yoshi's Egg (Egg Lay victim)
0F2 Enlarge(and Size Revert)
0F3 Shrink(and Size Revert)
10B Unloaded
10C Taunt(All 3)
10D smash taunt?
*10E Entrance
*10F Victory(All)
*110 Loss
111
112 N-Special
113 S-Special
114 U-Special
115 D-Special
116 FS
117- Special extras (eg 117 Reverse Falcon Punch)
The character specific special action IDs aren't documented very well. Some of them can be found in use in either Brawl+ or Balanced Brawl so inspection of the code for those two projects could be of some help to someone wanting to utilize them. Otherwise, you really just have to fish for them, being especially aware that many specials use a series of action IDs for various specific purposes (for instance, Ness's Pk Flash uses different action IDs for normal termination and termination via colliding the undetonated Pk Flash with an object).
EDIT 1: More thorough documentation of smash action IDs added.
Do note that this is based off the list in one of the old sticky topics, just updated. I noted what I added not out of egoism but so you know the difference in sources (that is, my guess versus other guesses). If anyone has any other documented action IDs, I'll happily add them. Do note that a lot of my unknown action IDs with very poor descriptions are probably aerial actions... I didn't do nearly as much testing in the air as I did on the ground.
000 Stand
001 Walk
002
003 Start Dash
004 Run
005 Stop
006 Turn 1
007 Turn 2
008 Stop Turn
009
00A Start Jump
00B Jump
00C Second Jump
00E Fall 1
00F Fall 2
010 Fall Dissabled
011 Enter Crouch
012 Crouch
013 Crawl Forwards
014 Crawl Backwards
015 Exit Crouch
016 Land 1
017 Land 2
018 arial-atk lag
019 Land Dissabled
01A Enter Shield
01B Shield
01C Exit Shield
01D shield stun
01E Dodge (AA note: is actually the Spotdodge)
01F Roll Forward
020 Roll Back
021 Air Dodge
022 Spotdodge (AA addition, broken)
023 Spotdodge (AA addition, broken)
024 N Attack(and Combo)
025 Rapid jab? (AA addition)
026 R Attack
027 S Attack
028 U Attack
029 D Attack
Eternal Yoshi clarification:
02A Side Smash Windup
02B Side Smash Charge
02C Side Smash Attack
02D Down Smash Windup
02E Down Smash Charge
02F Down Smash Attack
030 Up Smash Windup
031 Up Smash Charge
032 Up Smash Attack
033 Air Attack(All)
034 Grab
035 Grabbing Enemy
036 Dash Grab (AA addition)
037 Holding Enemy (AA addition)
038 Pivot Grab (AA addition)
039 Hold
03A Grab Attack
03B Release
03C Throw
03D Grabed
03E Held
03F Held Damage
040 Escape
041 jump break (AA added)
042 Thrown
043 odd slightly duck downward (AA added) ???
044 odd landing animation (AA added) ???
045 Hitstun
046 Hit ground
047 Hit wall
048 Hit ceiling
049 Tumble
04A Hit ground (tumble)
04B Hit wall (tumble)
04C Hit ceiling (tumble)
04D Lying
04E tech roll from lying on ground (AA added)
04F struggle on ground a bit (AA added)
050 tech roll from lying on ground (AA added)
051 get up
052 tech roll from lying on ground (AA added)
053 get up attack (AA added)
054 bounce on ground (AA added, speed up to remove jab locks)
055 hit ground hard (AA added)
056 broken shield that flies up (AA added)
057 hit ground hard with broken shield (AA added)
058 hit ground softly with broken shield (AA added)
059 get up from lying on ground with broken shield (AA added)
05A shield broken dizziness (AA added)
05B recover from broken shield (AA added)
05C fall asleep (AA added)
05D something in the middle of sleep (AA added)
05E wake up from sleep (AA added)
05F stunned from Deku Nut (AA added, mistaken for Mewtwo's Disable state haha)
060 tech (gound)
061 tech roll
062 tech (wall)
063 tech jump
064 tech (ceiling)
065 run into a wall (AA added)
066 strange compress thing (AA added) ???
067 footstool the enemy (AA added)
068 face the screen (AA added, can still do moves toward screen, WAY too cool) ???
069 odd really quick landing effect (AA added) ???
06A t-pose's Toon Link briefly then landing effect (AA added) ???
06B Mr. Game & Watch tpose's briefly and is then all black, no outline (AA added) ???
06C t-pose's Meta Knight briefly and then landing effect with eye glimmer (AA added) ???
06D quick jerk and then landing effect (AA added) ???
06E get footstooled on ground (AA added)
06F brief odd thing (AA added) ??? [helpless fall state in air]
070 get footstooled in air (AA added)
071 flop down hard on ground (AA added) ??? [spinning helpless after being footstooled in air?]
072 soft landing effect (AA added) ??? [falls really fast in air]
073 begin to grab ledge (AA added) [if forced in air, puts you in fall1 state with aerial jumps restored]
074 ledge grab
075 ledge hange
076 soft landing effect, probably some ledge action (AA added) ???
077 on ground for one frame, probably a ledge action (AA added) ???
078 soft landing effect, probably a ledge action (AA added) ???
079 ledge jump
07A ledge jump, perhaps 100% plus (AA added)
07B interesting pose for 1 frame, probably a ledge action (AA added) ???
07C begins to teeter off a ledge (AA added)
07D teetering off a ledge (AA added)
07E lands on ground hard (AA added) ???
07F freezes the game when Meta Knight tries it (AA added) ???
080 some sort of landing effect (AA added) ???
081 t-pose -> center of stage -> on rear end for a moment (Subspace teleport?) (AA added) ???
082 freezes the game when Meta Knight tries it (AA added) ???
083 big smoke cloud landing effect (AA added) ???
084 flop on ground and land on stomach (AA added) ???
085 freezes the game when Toon Link/Mr. Game & Watch does it (AA added) ???
086 get up from lying on stomach (AA added)
087 Toon Link t-pose's and then lands on the ground softly, Meta Knight makes it look like it's related to gliding (AA added) ???
088 Toon Link t-pose's and then lands on the ground softly, related to gliding (AA added) ???
089 trip on rear end, running over banana peel activates this (AA added)
08A related to tripping on rear end, getting hit by Diddy Kong's banana peels inflicts this (AA added)
08B turn around and trip (AA added)
08C fall forward and trip (AA added)
08D on the ground in a tripped state (AA added)
08E get up from tripped state (AA added)
08F attack from tripped state (AA added)
090 roll forward out of tripped state (AA added)
091 roll backward out of tripped state (AA added)
092 climb ladder
B4/B5: surfacing animation (same?)
B6: treading water (good health)
B7/B8: actively swimming (as in swimming forward) [no evidence B8 is used]
B9/BA: turning around in water [no evidence BA is used]
BB: floundering (about to drown)
BC: drowning
C7: Enter grounded state
C8: In grounded state
C9: Exit grounded state
CA: Frozen state
CB: Exiting frozen state
0BD Death
*0BE Respawn
EC: In Yoshi's Egg (Egg Lay victim)
0F2 Enlarge(and Size Revert)
0F3 Shrink(and Size Revert)
10B Unloaded
10C Taunt(All 3)
10D smash taunt?
*10E Entrance
*10F Victory(All)
*110 Loss
111
112 N-Special
113 S-Special
114 U-Special
115 D-Special
116 FS
117- Special extras (eg 117 Reverse Falcon Punch)
The character specific special action IDs aren't documented very well. Some of them can be found in use in either Brawl+ or Balanced Brawl so inspection of the code for those two projects could be of some help to someone wanting to utilize them. Otherwise, you really just have to fish for them, being especially aware that many specials use a series of action IDs for various specific purposes (for instance, Ness's Pk Flash uses different action IDs for normal termination and termination via colliding the undetonated Pk Flash with an object).
EDIT 1: More thorough documentation of smash action IDs added.