Re: Is it possible to amalgamate bookmarks from 2 different backup files?
Are that JSON backups or HTML backups?
You can easily merge bookmarks by importing each of the HTML backups, but restoring a JSON backup will always replace all the bookmarks.
So if you have a JSON backup then you need to export existing bookmarks to an HTML file and restore them.
An alternative to merge bookmarks is to use two profiles and restore a JSON backup in each of them.
Use Copy in the Library (Bookmarks Manager) of the second Firefox instance to Copy selected bookmarks to the clipboard and Paste them into the Library of the Firefox instance opened with the default profile.
You need to start the second Firefox instance (profile) with the -no-remote command line switch.
Without the need to setup a second profile Open a second copy of the library in tab or window by using this in the address bar chrome://browser/content/places/places.xul That may help with dragging and dropping from opposite ends of a long listing. If for example HTML has just been imported in to an already large bookmarks library.