You can make a Mapped Key that uses a Mapped Key State Action to toggle FTL Assist Me. It can be 1 step with it set to Toggle, or 2 steps with one Mapped Key State Action to turn it off, and one to turn it on in step 2. The 2 step method will let you also use a Popup Text Action, or Sound Action, to give you a visual or audio indication (or even a click bar button indicator)