Toolbar button to change what action a shortcut key triggers

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Hello - after a deep dive in REAPER's forum search, I have found a lot of related queries but only one that's talking specifically about what I want:

https://forums.cockos.com/showthread...33#post2490233

In ideal use scenario, I'd click a toolbar button, which would change color so it's clear that this alternate shortcut mode is active.

A good example would be for slip editing multitrack drums. I want to use a different action to split items than I'd normally use in the rest of my work. This toolbar button could allow me to use my usual "split" key.

I'm willing to do some legwork on this, but I am just starting my journey to learning lua and scripting for REAPER, so I'll need to start by pirating some code snippets. In the prior thread, Xenakios posted a link to some Python code he was working on, but the link is dead.

Any help would be greatly appreciated!