I couldn't agree more with this suggestion. The tree architecture is somewhat unintuitive and requires a lot of experimenting for new players as well as a lot of patience for advanced ones, when trying to work around issues like building wings, stacking things between multicouplers or even attatching large boosters (with tons of struts). The welding option Ricardo mentioned however might not be the ultimate solution, as you could just weld together your whole plane, which is just asking for stronger attatchment points. An update like the original post suggested however could be a major improvement in Kerbal rocket building, and is also in line with the major upgrades for vehicle building of the last and next update (Gizmos, Plane Building UI). Would be really great if something like this became reality in one of the next updates!
