in novas data file you can combo keymods with bubas function Nova_Mod()
it is a hex based system that you'll need to put the higher numbers at the top of the rotation
works like this say you want lshift and lctrl
if Nova_Mod(3) then return true end
if you want lshift and rshift it looks like this:
if Nova_Mod(9) then return true end
it opens up more key combos