Defining sub-admin role that can add URLs to be blocked, but isn't allowed to remove URLs from block list

Hi Sacha Roland 

Please refer to the article to create various admin profile- https://community.sophos.com/kb/en-us/126703 but unfortunately, specific requirement of yours cannot be achieved.

For Web and Content filter, we have None, Read-Only, Read-Write options but not specific to your requirement. You can submit your idea to https://ideas.sophos.com/