Hi Martin,
1). Glad that the usage and purpose of the extra "appearance" post types, is clear now.
To show the related posts, you'll find good examples from the single content templates that I've created on my test website:
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Please note how for relationships where only one related post can exist, I've used "item" attribute method:
https://toolset.com/documentation/user-guides/views-shortcodes/item-attribute/
Screenshot: hidden link
And for relationships where multiple related posts can exist, I've used the post view method:
Screenshot: hidden link
2) & 3). During troubleshooting, I was able to reproduce this issue on my test website as well.
It turns out that the "The Events Calendar" plugin filters all event post queries on the website and removes the past events.
( it doesn't distinguish if the query is from their own plugin or from a different plugin or theme )
On your test website, only one event "DUCHY WORKING GUNDOG CLUB" is shown in the drop-down because that is the only event whose date hasn't lapsed.
Screenshot: hidden link
You can get in touch with their support team and ask if there is some code or option to make it stop filtering past event posts.
If they're not able to assist you with this, then you can consider switching to a different events management plugin.
4). Your understanding is correct and each person participation post represents a single record/entry for a person's participation in a specific role in a specific event.
5). If you would like to show multiple fields from a different dog than the current one ( in this case current dog's sire and dam ), you can use a post view to change the scope of the current dog through a post view and passing on the required dog's ID, as a attribute in the view's shortcode.
( similar to what we've discussed a number of times in the past )
You'll create a new post view for example "View to show dogs, related sire and dam - single dog page" and set it to show only that one dog post, whose ID is passed in the view's shortcode attribute.
( screenshot: hidden link )
Any information that you'll show through that new view's loop, will come from the targeted dog and not the current dog (whose page is being viewed).
After that, you can pass on the current dog's sire and the dam post IDs to that new view like this:
[wpv-view name="view-to-show-dogs-related-sire-and-dam-single-dog-page" ids="[types field='dog-sire' output='raw'][/types]"]
[wpv-view name="view-to-show-dogs-related-sire-and-dam-single-dog-page" ids="[types field='dog-dam' output='raw'][/types]"]
I've added this new post view and its shortcodes in the single dog page template on my test website for clarity.
Important note: Since now that we have a better understanding of the new structure, I'll suggest starting a new ticket for each new question or concern.
( you can mention in those new tickets that it is related to what has been discussed in this thread )
regards,
Waqar