Problem:
How to connect WordPress users with other post types?
Solution:
The workflow should like these:
1) User register and login into your website
2) Show him "my account" page,
3) In this my account page, display a view block:
- Query "Member" posts
- Filter by post author is same as logged in user
- If there isn't any result found, show him a post form for creating "Member" post
- If found a result, show the "Member" post information
4) In the single "Member" post, display a post form for creating "registraties" post, in this post form display the post type relationship field
Relevant Documentation:
https://toolset.com/documentation/user-guides/views/filtering-views-query-by-author/
