And briefly speaking: there is no such feature in SU as "stacking order" or "send back" etc. like there is in 2D applications (where there is no other way of solving the problem). SU is meant to be used in 3D where everything has some thickness or at least some distance from another object just like in "real life" and this should (ideally) prevent Z-fighting.
A solution can be that you set these objects to cut a hole (i.e. "hide" what's underneath) but that also has its limitations as SU can only cut a hole on a raw face (and one face at a time) so if you are trying to put one component onto another, it will not work or if you want an object to cut a hole on two, adjacent faces (like in your example image), it will not work (only on one of them).
So try to work in real 3D instead.
