Some UI pannels cannot be bound with modifier keys, such as character screen

I rebound a lot of keys, and a common thing I do is that I want anything that opens a UI panel to never exist on the same plane as movement and spell binds.

So let's say I want to put all the UI pannels z,x,c,v,b. But I also want some spells from the second bar to be z,x,c.

So I want to put the UI pannels ctrl+z, ctrl+x, etc.

Most work, some do not. Character screen simply refuses to bind to ctrl+anything.