How do you do this? ive seen it done before, so i know its possible.
More than 1 undercombo on each screen
Use secret combos. Wherever you need a second undercombo, put a secret flag cooresponding to the undercombo you want there.
also, If you are using push blocks, put whatever you want as the undercombo on layer 1. This also applies for wherever you want to push that block, if it's push-inf