It takes a while, but the current system works for me.

I usually do a lot of map-work in the editor, then test it out every two hours or so. I then write down every issue I've seen, and then make the necessary changes. Presto, you're not switching too often between the editor and the testing mode.

Also, I use the X/Y/Z coordinate system often, so I can place components exactly where I want them. For example, if I want a row of walls extending from left to right on the map, I set the Height to the same, and the Up/Down to the same coordinate values. Then, I just tinker with the Left/Right values to create a long, precise wall.