Won't fix
The Event Espresso plugin adds an event post type (slug espresso_events) which can be connected to other post types using Toolset relationships.
But when editing such an event, the post relationships UI is missing, so it is not possible to see the connected posts or connect new posts.
This occurs because the plugin uses a custom admin page to edit its posts. Although it looks more-or-less like a typical WordPress post edit screen (classic, not Gutenberg), note that the URL points to admin.php and not post.php (used by all post edit screens, whether standard post types or custom post types).
The Toolset related posts UI only works with normal post edit screens (via post.php).
We don’t have a solution, other than to suggest contacting the plugin authors to see if they can provide code that allows editing event posts using the standard WordPress post editor.
