Tags are marked as used the first time they are referenced from any code of your application.

The fact that a previously used tag becomes no more used in the application is not automatically detected.

An updated of tag usage status can be requested with menu Tools / Update tag usage. The usage status is cleared and the application is scanned for actual tag usages.

This update could be useful to delete unused tag or to edit a tag (because some changes to tag are not allowed when it is marked as used.