Adding a column to Classification Store Relations

I’d like to add two checkbox columns to the Relations grid shown in the screenshot on the right side, and I’ve been struggling to figure out how to do so. It’s important that the values apply to the specific group-key relation rather than the key itself, which appears to be how the “Mandatory” field works. If the answer to this has something to do with Grid Configuration, I could not find where that is in Pimcore. Any help would be appreciated!