I would like to request that you check whether the player is wearing a Quark Backpack, and if true, move the buttons up by about 30 pixels (configurable preferably)

The reason I would like this is best described by this picture:

The orange section is the backpack inventory that is added when the user wears a Backpack

This also already happens without the backpack. If Quark is installed the buttons are on top of each other:

(The overlaid button is the one from quark)

should be less of an issue now, use the offset buttons to manually tweak position, if that doesn't work open a new issue

hardcoding for every single mod simply isn't possible nor feasable

True, worth a shot though :P
The offset works, thanks.