Admin search always showing

Yes. The “Use Relevanssi for admin searches” setting only applies to the search in the “Posts” list.

To control who sees “User searches”, use the relevanssi_user_searches_capability hook. The default capability here is edit_pages. For “Admin searches”, the hook is relevanssi_admin_search_capability and the default setting is edit_posts. If you want only Administrators to see these features, set the capability to update_plugins:

add_filter( 'relevanssi_user_searches_capability', function() { return 'update_plugins'; } );
add_filter( 'relevanssi_admin_search_capability', function() { return 'update_plugins'; } );

You can’t hide the features from admins this way. You can unhook

add_action( 'admin_menu', 'relevanssi_menu' );

But this will also remove the Relevanssi settings page.

Thank you! The filters worked great.