Custom Selector in Application Access Policy

In my work zero trust account, when creating a policy for an application, under ‘Create Additional Rules’ I see selectors in the drop down which are not Cloudflare default, and were created by previous admin. Their are more than in the list here and have custom work related names.

I can’t find how they were created to be included in the dropdown not sure how they were created. Can someone point to the documentation how to create those and what are the possible custom options available.