Actually, iirc, dsmash connects as a combo with nair, so if you manage to land a nair you can combo it into a dsmash. Can be nice to send the opponent off stage when they're not in kill % yet.
Just double check that it does combo. I can't recall well enough now.
It does so even at 0% yes.
Just checked it.
Fresh Nair starts to knock the opponent away at higher % but the late hitbox keeps them close enough for it to true combo as high as 100%+ if you have a running start into it.
EDIT: I've been able to get at as high as 113% using the weak hit of Nair on Pikachu, you may be able to push this like 5% higher but the window becomes
very tight to get the D-Smash out before they fly out of range.
I'm testing this with Pikachu, btw.
Pikachu because I just went random in training mode.
EDIT 2:
Running Late Nair -> F-Smash
true combos on Pikachu as high as 140% and maybe more.
Due to Pikachu's height this will start connecting at around 85% because before that he'll actually end up sliding just under Ryu's foot because the % isn't high enough such that he'll actually be lifted high enough off the ground.
Running fresh Nair at what seems to be the last possible frame before the ground true combos into F-Smash on Bowser as low as 20%.
I'll be testing all the other characters here in a minute.