When you use a shrinkwrap modifier and move a vertex, sure, the vertex moves along the target surface. But you moving the vertex doesn’t actually move it along the target surface. The modifier just fixes your position by running its algorithm to snap it to the closest part to fix it. This is a problem for me because my target surface is a curvy surface like an oval, and if I move the vertex far enough in a certain direction, it unexpectedly snaps to a different part of the target surface (because it actually IS closer to that part of the target, you just don’t see it because it’s the location before the shrinkwrap occurs which determines where it will be closest to and snap to).
So doing the shrinkwrap modifier does make sure that it will snap to the surface in the end, but that leaves the problem where moving the vertex too far off from the surface can make it snap to a different/closer part of the surface that you don’t want. I want the vertex to actually be sliding along the surface as I move it so it doesn’t teleport to a different part of the target surface unexpectedly.
If only I could somehow apply the shrinkwrap modifier after every time it executes, but automate that. That way the vertex is always on the target surface. This method does not sound ideal of course but I just wanted to give an idea of the kind of behavior I want.