I finally used the Mesh Editor and I really like it. Is there a Forum spot specifically designated for it? I have not seen too much info on it since a while ago when it was being used to model a lighthouse in VR.
For sure though the First thing it needs is exact control of everything ( and get rid of that grid that pops up). If I want to extrude 1 mm I need to be able to extrude 1 mm and be able to type in an exact value. This needs to be for all tools. That one feature will make the tool infinitely more useful. Right now you just have to eyeball everything. Also, add a distance display showing how far you are moving or scaling etc stuff. It is in the log but something on screen would be better.
Then after that:
1 - Being able use a reference object for the extrusion size, moving, scaling etc…
2 - Grouping Triangles and make them appear to be one face. I know I can hold Command and select multiple triangles but it would be great to be able to group them to perform operations on the group now and then later on.
3 - Union, Subtraction, Trim etc…
4 - These tools once stable should be added to the Static Mesh Editor too. That way if you just want to model on one object, the rest of your Scene is not in the way.
5 - Make tool icons and just add these to the standard toolbars at the top. They will become some of the most used tools once they are ready.
6 - Loose the grid that pops up when you select a triangle like one of the other guys said.
Some obvious problems:
1 - Crashes a lot 
but I imagine that is why it is not on by default. It really hates Draw vertices. Crashes every time. Not even sure what that does.
2 - Mesh Editing a Primitive messes up the primitive in that project. It needs to not effect the master. Hmm this seems to be WAY worse. editing any of the primitives or the ground in any project messes up the master…I have to fix my Cube now…yikes and I really screwed around with it lol. Is there a way to reset the Cube to its original form?
3 - The transform moves slow and then jumps too fast sometimes.
Further in the future
1 - Allow drawing of shapes on Planes that can then be extruded , scaled etc… Maybe that is what polygon is for but it doesn’t seem to work
What is so cool to think of is that you already have the best rendering engine and now all this needs is a couple new features and WOW.