Man this code is a mess! Haha. I might just completely redo this in Raylib or make it run in the browser, honestly, the keyboard shortcuts are all weird and could be replaced with checkboxes saying which parts you want to interpolate.
All in all I think I will return to this project in a couple months time (I have a couple other in queue right now) but thanks for taking the time for leaving the suggestions! I’ll add these to the feature list of the newer one, when I get to it.