Sometimes, you need to delete a data entity from the data entity master.  Sometimes, that's a pain to do because it's referenced in a data project, and you have to delete that reference before you can delete the master data.  Sometimes, you have hundreds of data projects to go through, and it sucks a lot.

You can always use table browser, lookup the DMFDefinitionGroupEntity table, and filter on the entity you're trying to delete to find the data projects to resolve.