Scott, there is a (not-so-simple) way, that I know, to rename planes.
1) Go to Results >> Planes.
2) Go to View >> Selection List. A box will now be visible with all your existing planes.
3) Double click on the names and rename.
I know the easiest and most logical way is to give an option to rename in the tree, but then, you can't have it all!
Try logging this to Idea Station. Maybe it will be considered for future iterations.