They are bound to I, O, 0, but they don't seem to work. Am I missing something?

Minecraft 1.16.3
ReplayMod 2.4.5

2.4.5 is not 2.5
New features and major changes will generally go into 2.5 (MC 1.16.3 support being the notable exception cause it only required minor changes and is somewhat time sensitive), which is still WIP.

(Side note: being bound to 0 means not being bound by default. It's not the same as being bound to Keyboard.KEY_0)

My bad, I thought closed issues ship immediately..