Since I'm a noob, i migth answer wrong, but also I encounter alot of problems So I'll try to keep this updated... Most answers I get from tutorials/members on this forum, so I take no credits for finding the answers.

Q: How do I show border edges as a thick line?
A: Click on Display > Polygon Components > Border Edges. You can also click on Display > Custom Polygon Display (Option box) and then decide the width of your edges by changing the "Edge Width" attribute.

Q: I display border edges When I put together a model of 2 halves and merge the vertices, the edges between still looks thick. How do I make them go away?
A: There is an easy fix for this. Select your Polygon. And click Polygon > Cleanup (Option Box). Check off the "Nonmanifold Geometry" and then click Cleanup and it should be fixxed.

Q: My undo list contains a limited number of undos, is there anyway to make this list bigger?
A: Yes, you can increase the number and even make the list infinite. Just click on Window > Settings/Preferences > Preferences... . Then click in the list where it stands "Undo" and you can chose infinite, or the length you want of a finite undo list. I'm using infinite numbers of undo, and I haven't noticed it slowing down my computer.