I want to implement a dash feature like Celeste (except only forwards and backwards) but my player is affected by gravity. Can I change my physics using a behavior block or not?
Well, there is a behavior called “Material” that allows you to change friction, density, and bounce, but that is it.
If you want to manually change the Gravity specifically of that object, then look at this discussion:
Density and friction can be changed with the behavior SuperStarGames just mentioned.
That goes off of the value of 100% of its current property
(so like friction is at 40, 100% is between 0 to 40).