For example if I want an item to jump when I want, just use:
item 1 vspeed = -50
For example, that will give vspeed -50 to item 1
This should work for other stuff
enemy 5 hspeed = 20
player 1 hspeed = -30
Note that this shouldn't be terminal speed, it's only a force speed. So for example, giving vspeed to a player to make it go up, will only set the speed for that moment. Afterwards, the gravity will do it's old trickery