s3rg385 That's a great way to do 3D editing with the 2D editor! I'm interested to see where you go with it.
My workaround for 3D editing is to set up incremental "set position" keyboard-activated movements for all six directions (increments of 1, 5 or 10) for each 3D object in the Event sheet, and then I go to the Preview window (the 3D view), press the arrow buttons, etc., to move the object around until I get it into the right space. The increments are recorded in text objects representing x, y and z. When I've got the object where I want it, I write down the coordinates from the text objects, go back to the 2D editor, and change the object's coordinates accordingly. I used this also for having a character reach for an object and touch it precisely with his hand. So far it's worked pretty well.
I'd like to combine that technique with the one you came up with, to speed things up. Thanks for the information! (Unfortunately, I'm not with my Construct 2 right now, so I couldn't work on the problem you have--making the walls solid. I was able to do it before, but that was using a different view orientation from yours (with y as the vertical axis, z as depth, x as width).