Currently disabling an add-on removes it's preferences.

Users may have many options for an add-on which they don't want to loose when it's disabled.

See T71451: Support for keeping preferences of disabled add-ons for a report on this issue.

Proposed solution:

• When disabling an add-on which has preferences, keep the preferences instead of freeing them.
  
  Internally this could be a list of disabled add-ons, used to restore the preferences when enabling them later.
• Add button to add-ons with preferences to reset preferences.
  
  While not essential, without this there is no way to reset an add-ons preferences, where there was beforehand.
• Add a drop-down menu (replacing the current refresh button) which has a menu item to remove all unused add-ons (to prevent accumulation). This menu will contain the "Refresh" button too.
  
  Exact details for the UI can be changed, suggest to replace the "Refresh" button to avoid too much clutter for actions that aren't used often.