The BEST improvement to folder management would be to support Drag & Drop in the main inbox screen, and have the folder list implemented as an actual TREE instead of a list that has to be repainted after an edit is made. (I know that in WebClient theme, you can add/delete/rename folders right on the inbox page, but it repaints the folder list after you do that and then you lose your place.)

BUT if that is too big a change, please consider improving the utility in just the folder management page: Please make the list of folders we are managing into an actual TREE control that can be collapsed so that you do not have to scroll through many many pages of listed folder names to find the one you want to edit. AND: If you are "Renaming" a folder in order to place it inside another folder: Please make that folder selection list into a tree as well, for the same reason.
And last: Let the edit take place without repainting the entire tree after the edit is complete, so you do not lose your place in the tree.

Last: It is un-intuitive to have to "Rename" a folder when what you really want to do is Move it.

Really, the entire Folder Management concept in WebClient needs overhaul, so I understand that it may be difficult or impossible to do any one of these improvements individually.

I implore you to undertake this overhaul in both the Lookout and WebClient themes. This is really worst weak spot I find in using the WebClient interface.