Page categories

As stated in the documentation (Custom Variables Analytics - Analytics Platform - Matomo “common use cases” ) categories in piwik are done using custom variables, but there are some limitations to that.

Is there a way to group pages after they got tracked? To define categories in retrospective? E.g. I wanted to add the pages with pagetitle “startpage”, “page1”, “page2” to a category and see the joined tracking stats.

Also, it would be good if that can be done in the UI.