Can't find Folder-Account setting

The folder-account for Local Folders has changed, without me doing it. I want to be able to set the folder again. Where are the settings? I don't see them as an option when I right-click on a folder, or in the Tools/Add-Ons Preferences.

Thanks for your help,
Steve
thunderbird 60.8.0 (64-bit) on Ubuntu 19.04