Drag and drop onto bookmark icon no longer works Firefox 120.01 (2023)
Two computers. Both computers name version of Firefox and same version Of Windows 10. On computer 1 drag and drop no longer works. I can click star next url and manually to bookmark toolbar. I also cannot reorder on tool bar by dragging and dropping by selecting.
How do I know I'm doing it correctly? On computer 2 it works exactly as should. Click on padlock and drop or click on entry and toolbar and reorder. Same extensions etc and do not have a bookmark extension though have tab session manager. Same version both computers. Only difference in browser is number of tabs open. x 10 difference in number of tabs open computer 1 versus 2.
If I put firefox in troubleshoot mode with extensions etc off or create a brand new profile and try same problem.
Opaite Mbohovái (4)
May have found solution though solution is 10 years old. "ESC" worked for me too. I also did an outlook.exe/clean prior to the problem. Absolutely amazing.
http://it.thelibrarie.com/weblog/2010/06/drag-and-drop-stops-working/#google_vignette
On this part "I also did an outlook.exe/clean prior to the problem. " Never mind.
You can drag the Bookmarks Menu button 
that shows the bookmarks in a drop-down list and drag the Library button that gives access to recent bookmarks and history from the Customize palette to the Navigation Toolbar.
The Bookmarks Menu button has a "View bookmarks sidebar" menu item.
See "How do I add the Bookmarks Menu button to the toolbar?"
Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile. Make sure you stay signed out of your sync account when testing.