it would look something like this. this will make you descend at 2x the normal rate.
on spacebar pressed
subevent: player is on floor >>> normal attack animation
else >>> set vector y to player.platform.maxfallspeed*2, set animation to "falling swing"
is playing "falling swing" >>> set animation "smash"
note: gravity should be set to half of maxfallspeed for this example, and jump strength should be adjusted for the gravity.