The bookmarks you move around in the Library,from folder to folder,doesn't end up the way you want them to.
I was looking for something like the developing-team to let them know that they once again forgot about this issue,but this was all I could find,so...any ideas? Example: You move a couple of bookmarks from one folder to another (CTRL+X / CTRL+V) which already contains bookmarks - for example to the bottom of that folder,but that doesn't really matter - some of them end up at the bottom,while some end up somewhere else in this folder,among the other bookmarks which were already there - one bookmark which should be highlighted/among the ones you just moved is no longer highlighted - instead another bookmark,which was already in that folder,is now highlighted together with all the others you have moved...so there's really more than one issue connected to this issue. The same thing occured a couple of updates ago,but went away after the next update.
Wšykne wótegrona (1)
You could file a bug, that's probably the most direct route to reporting a specific technical problem.
But before reporting, could you reproduce it in a "clean profile"?
First, make an extra backup of your bookmarks in a convenient location, such as Documents. This article has the steps:
Restore bookmarks from backup or move them to another computer
Next:
New Profile Test
This takes about 3 minutes, plus the time to test the Library.
Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.
Click the Create a New Profile button, then click Next. Assign a name like Nov2017 or TEST, ignore the option to relocate the profile folder, and click the Finish button.
After creating the profile, scroll down to it and click the Set as default profile button below that profile, then scroll back up and click the Restart normally button. (There are some other buttons, but please ignore them.)
Firefox should exit and then start up using the new profile, which will just look brand new. If Firefox asks about enabling extensions it discovered, just leave those disabled for the time being.
To restore your bookmarks into this profile, see the earlier article and use the "Choose File" option to access your fresh backup.
Does the problem reproduce in the new profile?
You may want to exit Firefox and start it up again once and repeat the test in case there is any difference after Firefox does it multiprocess detection and other "first run" procedures.
When you are done with the experiment, open the about:profiles page again, click the Set as default profile button for your normal profile, then click the Restart normally button to get back to it.