How to set build button to R2 (Steam Deck)

[rbits]

I want to set the build button to R2, because I can't use the trackpad and press A at the same time. But when I try to set build to R2, it says "This control has to be from A or X". Why is this? I can set other controls to R2, but not build.

If it can't be done in the game normally, is there at least a mod that lets me customise the bindings?

I know I can remap it in Steam Input, but then that would change the button in all the menus as well, and that's not ideal.