I'd like to be able to rebind the various IDE actions to different keys, as some of them are frustrating for me to use.  This includes the capacity to bind multiple keys to the same action, and multiple actions to the same key.

Normally I don't like presenting my own personal case that prompts these general requests, but I feel like this time it won't detract from the original argument.
I personally need to rebind the keys for the SFX editor, because the “piano-like layout” for typing notes is impossible for me to wrap my head around, to the point where I genuinely can't use it.  I can show you what I mean if you want, but remember that the request is for everything to be arbitrarily rebindable.

This doesn't answer your question about allowing general re-bindings, but maybe this will help clarify the layout for the SFX editor's "piano-like layout"?

@MBoffin
Oh, I know exactly what the keybinds are.  I mean I can't wrap my head around a piano in general, because of how I understand music and sound.  I was going to change it to an isomorphic layout, if I could (and rebind whatever else this would spill over).
It's not the only thing I'd change, but I feel like I can't express my urgency for this without explaining myself.

I'm going to show the default layout just so you know how I color coded this.  (Using numbers instead of the standard notation because even my smallest font doesn't fit more than one letter on the keys in this image.)
I know the colors I used here seem odd, but it shows why I find this uncomfortable to work with.

I'd have changed it to one of these.  These being upside-down versions of a Jankó keyboard, and the Wicki-Hayden note layout which is used on certain concertinas.

(and before you ask, the keyboard sprite is an old to-scale model I made of the keyboard I have, so I can't exactly resize it)

EDIT: Apparently PICO-8 has a hidden 3×4 font in it, I should clarify that I didn't use this. I used an incomplete 3×4 font I'd made years ago before I ever had PICO-8.

EDIT 05/19: I noticed that I got the Wicki-Hayden layout messed up, so I've fixed that now.