every time you need a parallel process for the entire game , copy it from the normal parallel process, put it as a common event and set it's trigger to parallel proccess, choose a switch and turn it on first thing you do in the game
as for what you want, the parallel looks like that:
(no need for the switch since you will use the one that turns the common event on)
if button L is pushed then
-move event: player(change speed: 6)
-if switch frog=on then
--move event: player(change graphics: frogrunning mode)
-if switch anything else=on then
--move event:player(change graphics: anything elserunning mode)
else
-move event: player(change speed:4)
-if switch frog=on then
--move event:player(change graphics : frog)
-if switch anything else=on then
--move event: player(change graphics: anything else)
every time you change the hero into something, turn a switch on so that you could command the event to change to what you want