add support to other custom variables beside the 3 BTT internal customVariables

Problem is, the BTT rule editor is currently not dynamic at all,

:pleading_face::man_facepalming:

I’d be interested in your usecase for this

basically so we dont have to do the group activation hack example, instead u set a custome variable according to the case you are working with & have a conditional group with some extra functionality that activates when that variable changes.