The trouble is.. Schefflera do not make for good bonsai, unless perhaps grown in the tropics where they develop trunks. The large compound leaves require a big trunk. What the lat picture shows is something that resembles a tree, but is actually a shrub on top of a rock, with the roots draped of the rock to simulate a trunk. So even in Hawai it seems they do not manage to grow trunks fast enough?
In Michigan (That's where the OP is?) schefflera will not within the next few decades grow a trunk to speak of. And in the dry air, air roots will hardly develop. So it is much better to look at another species, and just grow this as a houseplant.
Junipers, pines, maples, oak, beech are all species that respond well to bonsai training, and are native to the michigan area. As such, they will do best there. There is something called zone envy: People wanting to grow species that are not suited for their climatic zone. In the end it almost always results in disappointment, small underdeveloped trees without a trunk and open canopies. Grow species that do well in your climate. I might soon be given an cork oak by a friend who lives another 400km noth of where I am. The growing season at his place is too short for the oak. As I have a greenhouse, I can give it 2 months more, and it may do well. He spent a lot of time and effort picking this tree up in southern spain. But realized: It is too cold, dark and wet where he lives. on the long run, the most painfull decisions results in the best trees. So unless you do not want to get the best tree you are capable of growing.. Start off with the right species.