Made a bunch of fixes over the past few hours, and got the atmosphere tab working. Just need to add in the skybox selection, and it will be done.
This morning I fixed the object dragging, improving it beyond how it used to work in the old editor. The old editor supported view-space dragging, with optional X,Y,Z filters to restrict it along just one or two axes. This got confusing as you switched from top-down to first-person views.
Instead, I now have a horizontal drag, which always drags in x & z, but can be filtered with the X & Z keys, and a separate Y drag for vertical dragging.
The horizontal drag does some work to ensure that right on your screen translates into a X or Z translation that goes right on your screen as well, so it's partly view relative, but you don't have things moving in unexpected ways anymore.
Last night saw the addition of the Decal tab, and I also finished the mesh tab, this morning adding a 'force to size' option to set the desired size of the mesh manually, in addition to a 'relative scale' option to scale each of the x,y,z dimensions by a particular amount.
Last is adding in another rotation option, and also the vertex tab. I'm thinking of adding some more editing controls on the vertex level to automatically repel vertices from the mouse in certain shapes, like spheres and cubes. I could add a tension option, where after triangles got stretched too much, they would tesselate. This way you could drag a sphere through a heightfield and have the heightfield push away. If you dragged the sphere into the heightfield at a sharp angle, it would create a tunnel. Still thinking about it, but it seems something that may be doable without doing a full CSG or marching-cubes type of thing....
Here is a shot of a test level made in ~8 minutes from the new editor...