If you use Sync then best is to disconnect Sync temporarily during troubleshooting. You can check for problems with the <b>places.sqlite</b> and <b>favicons.sqlite</b> files in the Firefox profile folder. *use "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page In case errors are reported with "Verify Integrity" close and restart Firefox and retry. If "Verify Integrity" cannot repair places.sqlite, rename/remove all <b>places.sqlite</b> and <b>favicons.sqlite</b> files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder. *keep a backup copy of places.sqlite in case a new places.sqlite database has to be created See also: *https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file *https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page. *Help -> Troubleshooting Information -> Profile Directory/Folder:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US/kb/Profiles

The verify integrity returned no errors, tried deleting again and drag and drop. Still could not do either, opted to close and restart FF again, took 2 minutes for FF to properly close and restart. Success! I can now organize my bookmarks again.