If you do a jump-and-then-slide on the ground, it's a normal slide. But in the air it's a jumping slide. I think it only goes to the height of a normal jump, but haven't checked carefully. I've never had it happen on stairs; that's cool!
So kyletm57, I think what's happening is you're running slightly off the platform, and then pushing the jump button and flip button very quickly, so your slide comes out instead of the flip.
Relatedly, it's possible to do your ground moves (basic punches and kicks and rolls) while airborne. I've messed around with it a little but not enough to get the hang of it.
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