If you have sync, and there is a problem anywhere, Shut Down Sync Immediately On All Devices to prevent the problem from spreading. Type https://accounts.firefox.com/settings<enter> in the address box. Once the problem is fixed, perform the same repair on all computers/profiles before using sync again.

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address box.

You will find Places Database near the bottom. Press the Verify Integrity button.

If any errors are reported: https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

The places.sqlite file contains your History and Bookmarks. And it looks like it is corrupted.

Type about:support<enter> in the address box.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Locate the above file. Then rename or delete it. Restart Firefox. The browser should then create a new place.sqlite and recover your bookmarks from the backup files.

Note: Your history is not backed up and will be lost.

Hi FredMcD, thanks for your reply, I didn't have sync turned on, and drag and drop bookmarks in the side bar is still working on another of my macs 10.14.6 Mojave with Firefox 95.02 so it looks like the finger points at Monterey?

Verify Integrity > Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum + Initial database size is 5120KiB + The database has been vacuumed + Final database size is 5120KiB > Task: stats + Places.sqlite size is 5120KiB + Favicons.sqlite size is 1664KiB + pragma_user_version is 59 + pragma_page_size is 32768 + pragma_cache_size is -2048 + pragma_journal_mode is wal + pragma_synchronous is 1 + History can store a maximum of 47692 unique pages + Table moz_origins has 634 records + Table moz_places has 1541 records + Table moz_historyvisits has 890 records + Table moz_inputhistory has 0 records + Table moz_bookmarks has 2728 records + Table moz_bookmarks_deleted has 0 records + Table moz_keywords has 0 records + Table sqlite_sequence has 0 records + Table moz_anno_attributes has 2 records + Table moz_annos has 10 records + Table moz_items_annos has 0 records + Table moz_meta has 3 records + Table moz_places_metadata has 0 records + Table moz_places_metadata_search_queries has 0 records + Table moz_places_metadata_snapshots has 0 records + Table moz_places_metadata_snapshots_extra has 0 records + Table moz_places_metadata_snapshots_groups has 0 records + Table moz_places_metadata_groups_to_snapshots has 0 records + Table moz_session_metadata has 0 records + Table moz_session_to_places has 0 records + Table sqlite_stat1 has 16 records + Pages sequentiality: 69.9 + sqlite_schema: 32KiB (1.4%), 27.5% eff. + moz_origins: 32KiB (1.4%), 74.2% eff. + sqlite_autoindex_moz_origins_1: 32KiB (1.4%), 68.5% eff. + moz_historyvisits: 32KiB (1.4%), 63.2% eff. + moz_inputhistory: 32KiB (1.4%), 0% eff. + sqlite_autoindex_moz_inputhistory_1: 32KiB (1.4%), 0% eff. + moz_bookmarks_deleted: 32KiB (1.4%), 0% eff. + sqlite_autoindex_moz_bookmarks_deleted_1: 32KiB (1.4%), 0% eff. + moz_keywords: 32KiB (1.4%), 0% eff. + sqlite_autoindex_moz_keywords_1: 32KiB (1.4%), 0% eff. + sqlite_sequence: 32KiB (1.4%), 0% eff. + moz_anno_attributes: 32KiB (1.4%), 0.2% eff. + sqlite_autoindex_moz_anno_attributes_1: 32KiB (1.4%), 0.2% eff. + moz_annos: 32KiB (1.4%), 2.7% eff. + moz_items_annos: 32KiB (1.4%), 0% eff. + moz_meta: 32KiB (1.4%), 0.3% eff. + moz_places_metadata: 32KiB (1.4%), 0% eff. + moz_places_metadata_search_queries: 32KiB (1.4%), 0% eff. + sqlite_autoindex_moz_places_metadata_search_queries_1: 32KiB (1.4%), 0% eff. + moz_places_metadata_snapshots: 32KiB (1.4%), 0% eff. + moz_places_metadata_snapshots_extra: 32KiB (1.4%), 0% eff. + moz_places_metadata_snapshots_groups: 32KiB (1.4%), 0% eff. + moz_places_metadata_groups_to_snapshots: 32KiB (1.4%), 0% eff. + moz_session_metadata: 32KiB (1.4%), 0% eff. + sqlite_autoindex_moz_session_metadata_1: 32KiB (1.4%), 0% eff. + moz_session_to_places: 32KiB (1.4%), 0% eff. + sqlite_stat1: 32KiB (1.4%), 2.6% eff. + moz_places_url_hashindex: 32KiB (1.4%), 65.8% eff. + moz_places_visitcount: 32KiB (1.4%), 37.8% eff. + moz_places_frecencyindex: 32KiB (1.4%), 45.3% eff. + moz_places_lastvisitdateindex: 32KiB (1.4%), 52.3% eff. + moz_places_guid_uniqueindex: 32KiB (1.4%), 94% eff. + moz_places_originidindex: 32KiB (1.4%), 45.3% eff. + moz_historyvisits_placedateindex: 32KiB (1.4%), 51.1% eff. + moz_historyvisits_fromindex: 32KiB (1.4%), 24.4% eff. + moz_historyvisits_dateindex: 32KiB (1.4%), 43.1% eff. + moz_bookmarks_itemindex: 32KiB (1.4%), 90.8% eff. + moz_keywords_placepostdata_uniqueindex: 32KiB (1.4%), 0% eff. + moz_annos_placeattributeindex: 32KiB (1.4%), 0.4% eff. + moz_items_annos_itemattributeindex: 32KiB (1.4%), 0% eff. + moz_places_metadata_placecreated_uniqueindex: 32KiB (1.4%), 0% eff. + moz_places_hostindex: 96KiB (4.1%), 40.4% eff. + moz_bookmarks_parentindex: 96KiB (4.1%), 33.6% eff. + moz_bookmarks_itemlastmodifiedindex: 96KiB (4.1%), 52.4% eff. + moz_bookmarks_dateaddedindex: 96KiB (4.1%), 44.3% eff. + moz_bookmarks_guid_uniqueindex: 96KiB (4.1%), 55.4% eff. + moz_bookmarks: 224KiB (9.5%), 84.8% eff. + moz_places: 352KiB (14.9%), 85.2% eff. > Task: _refreshUI

Just going to try the places.sqlite deletion and rather than lose this reply, post it and come back again, bye for now.....:)

Many thanks, renaming places.sqlite has fixed it, thought verify said it was sane! Thank you again for your detailed reply.

I barely manage to keep my bookmarks under control anyway and use drag and drop re-ordering a lot, so restoring that functionality is very helpful.

I keep hoping that with each Firefox update that there will one day be a way to select multiple bookmarks for operations like deletion, or move or place in new subfolder, but it never happens, maybe one day....:)

Glad to help. Safe Surfing.

The Bookmarks Manager works much like the computer's file browser. Select the first item with a left-click. Then, holding down the <Shift> key, select other items the same way.

Ah yes so it does and it seems to have acquired the ability to delete multiple bookmarks too, that's great. Thanks once again.....