Hi...
I want to share my ten-minutes experiment results with you...
First, make a common event, call it anything. Make it parallel (the switch is up to you).
Make a conditional branch. Switch to tab 4 and activate the Script. Fill it with:
Input.press?(Input::SHIFT)
don't forget the else case.
Now, for the if case, make a move event. Player: change speed: 5.
For the else case: Player: change speed:4.
Sorry for the bad grammar and writing, but if you understand it, you'll find it useful.
Thx!