I recently upgraded to Linux Mint 17 Cinnamon, and am now running Firefox 31.
Recently I decided to clean up my bookmarks; my intention was to transfer everything in the "Recent Bookmarks" folder to folders dedicated to particular subjects. Unfortunately, if I cut/paste, the bookmark remains in "Recent Bookmarks", and if I delete it there, it also vanishes from the folder where I had copied it!
I have considered deleting the "Recent Bookmarks" folder, wondering if new bookmarks would simply pile up at the foot of the column as they once used to—but this might simply introduce a new problem. . .
Any advice?

The "Recent" bookmarks is a history which you cannot directly edit. But there is a folder called "Unsorted bookmarks" at the bottom of the tree view in the bookmark manager window. It lists all bookmark which do not have a place in the menu yet. I think you could use this folder.

Okay, thanks very much, I guess I'll call this solved.

It does strike me as a bit of a bug: the cut/paste options, etc, are not greyed out, so one expects them to do something.

I don't see much point in having both a "Recent Bookmarks" folder and an "Unsorted Bookmarks" folder (indeed, I don't see much point to either!) but no doubt it depends how you like to work.

In the interests of simplicity, I have simply deleted the "Recent Bookmarks" folder.