Problem fixed itself. For some reason it's letting me delete now.

Problem hasn't fixed itself for me, about half of the items in the right click menu are grayed out in bookmarks, I can't open in a new tab/window cut or delete a bookmark, those are all grayed out.

Close your browser and re-open it. You can now delete bookmarks. I think it may be blocked due to changing something in the menus and a restart of Firefox releases the menus for editing.

Under 'Bookmarks' - Show all bookmarks, opens the library, find and delete as you like (right click).

I had the same problem, couldn't right click and delete anything in a folder.

On the Bookmarks toolbar, click on the Bookmarks icon (far right), then scroll to the bottom of the list and select the last entry "Unsorted Bookmarks".

When the bookmarks list opens, go to the left hand column and click on Bookmarks Menu.

Now right click on the bookmark(s) you wish to delete and select Delete from the list of options.