I've been using this tool for a while now and I'm proud to say it's completely optimized my workflow. I always used to take me so much time to build environmental geometry because the 3dsMax viewport/rendering was never good enough to give me an accurate idea of what the end result would be. This is an absolutely essential tool and I love it in every way possible.
That being said, there are some simple additions/edits that can really help people save time with their work.
1. Planar Vertex Alignment - This may seem a bit complicated, but the implementation of it is actually surprisingly easy. The ability to select a group of vertices and align them all to an axis would be hugely beneficial to people making use of modular design or tilesets because you can eliminate vertex position error and seams with randomized/procedural generated content and tiling. There are several other benefits to this as well, but that was the main one that came to my mind. Another, quicker method to do this would be to give the user the ability to see and edit individual vertex positions. Right now I have to manually shift each vertex to make them align on a singular plane. It isn't life threatening, of course, but just something that would make a lot of lives easier.
2. Vertex Snap Edit - Currently, vertex snap works perfectly, so long as you're selecting just one vertex. If I want to get a group of vertexes to attach to another (with the same position offsets as the initial group) I have to spend a minute or so dragging the mouse around the target area until it locates the position that works. Ideally, you should be able to mouse over one of the selected vertices and use that as the anchor to snap with. The other selected vertices would just keep their same offsets to the anchor vertex, so that shouldn't be too difficult to implement.
3. Slice Plane/Cut tool - This one is a bit more complicated than the others, at least where the cut tool is involved. For the slice plane, it would be great to have the ability to slice a mesh using a simple plane who's dimensions you can edit in the probuilder menu/with the transform manipulator tools. Plane intersection is a lot easier to handle than a cut tool, though it would still be fantastic to have one.
There you have it, those are just some simple additions that I think would really improve the production speed for people.
Also thought I'd just introduce myself!