Map Manager doesn't do anything but point to the Downloads directory.
When in Basecamp, checked many of the menu options. Under Maps, found "Installed Maps Info..." That is where all the maps are listed. One of the options is to show the map in Finder. Did that and then deleted the map in Finder. The unwanted maps are now gone.
When in Basecamp, checked many of the menu options. Under Maps, found "Installed Maps Info..." That is where all the maps are listed. One of the options is to show the map in Finder. Did that and then deleted the map in Finder. The unwanted maps are now gone.