How do you hold your breath while aiming?

Long time player but recently switched from mouse and kb to controller after having some ergonomic problems.

I'm getting better at aiming with controller but haven't figured out how I'm supposed to hold my breath while aiming.

On my XBox controller, right trigger is to shoot while right bumper is to hold breath meaning I can't do both at the same time. I wanted to try switching the breath button to left bumper but I can't find a way to update the control scheme.

Curious if anyone else here is having the same struggle or how you got past it. The only thing I can think of is using my middle finger on the trigger but that feels so awkward.