In my inherited Gramps database is a multitude of unused placenames.
Is it possible to filter them on unused then batch delete them?
(I know I should backup first)
In Gramps ‘Tools > Family Tree Repair > Remove Unused Objects’. Untick everything other than ‘Search for places’ and then click ‘Find’ button. It will then list all the places that are not attached to people, events, etc. Select ‘Mark All’ button and then the ‘Delete’ button. You can rerun this as often as you like. As you said do a backup first as you cannot undo the process. Details are located at Gramps 5.1 Wiki Manual - Tools - Gramps (gramps-project.org)
After this you might want to do ‘Tools > Family Tree Processing > Reorder Gramps IDs’ . It is not essential, but I like to run this after I have deleted unused objects. Gramps 5.1 Wiki Manual - Tools - Gramps (gramps-project.org)
Good luck