In the hook_form_alter() function in your .theme file or custom module

I can only see 23 fields in total. Such as: Bulk operations: Content, Content: Add comment link, Content: All taxonomy terms, Content: Nid, Content: Path, Content: Post date, Content: Type etc. It won't show any fields pertaining to the node content such as body, or any other fields I've created or any content about the author other than UID. Whenever I delete the relationship I am able to see hundreds of fields that can be added.

Thanks, it works correctly. However, When I click "Add" for a field, I still cannot get anything other than the basic fields. Any insight into why views won't show me all available fields?

Sorry I'm a bit new here to Drupal. Am I suppose to copy this into somewhere?