Thanks for this! I have some stuff to google now. Great to hear that what I want is "simple" - I think it's pretty basic too :)

My AHK stuff is a bit more complicated - my scripts total about 5000 LOC, but a lot of that is inflated cause it also doubles as a window manager. It does a bunch of other minor stuff, e.g. Alt-IJKL also combos with Shift for selection and Ctrl for word skipping, but I'm sure xmodmap and other tools you mentioned can handle that.