Logi Options, One Handed Typing, FN Modifier Keys

So I'm trying to see if I can type while moving my hand as little as possible. I have to press the L and P buttons a lot while using certain programs and was basically trying to remap it so that If I use FN + F it gives me an L. Ideally I would use the side button on my mouse to give me the FN modifier, as pressing it with my left hand while reaching all the way to F isn't very fast or comfortable. I've tried using the Logi Options app with BTT but they aren't interacting at all. I tried mapping the side gesture button to turn on all other modifier keys within logi options and then in BTT mapped it so all modifier keys gives me FN but its difficult. I'd appreciate some help about how to better go about this. I really don't want to mess with the default modifiers because a lot of programs I use like Ableton and Pro Tools have loads of commands that I don't want overwritten. Thanks

Oh and yes I'v enabled Higher level modifier key recognition and restarted both apps.