As you are using the platform behavior, you can simulate controls right/left in an event platform is NOT on floor (same condition as your event 14 that you right click/Invert).
For the direction in which to go to, make an instance variable "Direction" to your object "joueur". When direction is 0, it means you want to go right, when it is 1 it means you want to go left.
Those will be subevents of the event mentioned previously.
To determine whether "Direction" is 0 or 1, you can place an imagepoint at the end of your "power" arrow and check its X position in relation to the monkey X position on touch end.
If the X of the arrow is greater then the X of the monkey, it means the player is orienting the arrow to the right, so "Direction" should be 0.
If the X of the arrow is lower than the X of the monkey, it means the player is orienting the arrow to the left, so "Direction" should be 1.