Why can't I change the Copilot key to Custom?

[Windows 11]

I had previously changed the shortcut to opening the calculator but after I had to reinstall windows, now it looks like this. It gives me no option except Copilot when I choose Custom. I've found posts about changing the Copilot key but all talk about changing it into Ctrl or a different existing key, that's not what I want, I just want it to open the calculator again

View the full article