Any way to use something like "sub-UV index" for Rich Text Image Decorators?

I’m trying to set up rich text image decorators to use when referring to gamepad buttons, so when I have an in-game message saying “press this button to jump”, the actual button icon is in the text.
I already learned how to do that, but I was wondering if there was a way to avoid having to create an image for every single button and instead have a single image with all the button icons spread in a grid and use it like a “sub-UV index”.

Can this be achieved somehow?