Hi, I personally would take some (5, 7) of them and from just above the trunk bottoms, wrap them together with something like raffia that won't damage the (eventual) bark, and if there are a couple of 'branches' lower down on the stems before the main branching, only wrap ~ 1/3 of it and let it hang out otherwise. They will eventually grow together (months to a year) and you'll have the beginnings of a trunk, vs just a sad little one trick plant (which Scheffleras will be if just grown alone). I'd also plant your wrapped stems each in its own (not too deep) pot and let it be for a couple of years, even if you unwrap the stems after a year to expose the 'trunk'. Once you have decent woody real trunks, then you can think about where you want to go with them - and you'll have plenty of time to decide that while you're waiting for them to grown up.