I think that I understand you. Let me reiterate just to make sure. You suggest selecting the vertex in 3d mode, then making the z-adjustment in the 2d view. That's pretty good advice, but I'm much rather have some built in function which makes it possible to constrain movement right in the 3d window. It would save me a lot of time.
Also, I'm finding difficult to keep the vertex selected in the 3d window. If I click on the vertex once, it turns red in the 3d view and becomes highlighted in the 2d views. However, when I release the mouse button, the vertex is no longer selected. I found a sneaky way to keep it selected: You can right click on it and choose "copy". Then it will remain highlighted in the other views.
Here's a picture to show you what I mean:
Even if there's some way to achieve what I'm trying to do, it sure would be nice to be able to do it right in the 3d view. Efficiency is a great thing while working on large levels.
Thanks!
- Bret