one option which would function as a global OR, would simply be to have assignable rows to outputs, where more than one output could be assigned to a row.
ie, by default each row gets an output-- represented easily by a diagonal. if i add a method for showing the mappings, you could easily assign row 2 to outputs 2 and 3 and 4.
again though, the “gesture” for getting into this mode is a bit nebulous. two right keys is probably the last one left.