ok - I understand now, this could be due to the posts where the "_wpcf_belongs_artist_id" column value is missing could be created after updated to new post reationship. With old (legacy) psot relationship we used to manage post-relatioin using postmeta key "_wpcf_belongs_artist_id" but that is not the case with new post relationship.
Toolset stores the post-relationship information in its specialized tables, which is why you're not seeing connection information in meta keys/custom fields.
To understand how to export the related posts information, you'll first need to understand how Toolset would expect it during the import process. The following guide on the topic will make this more clear:
https://toolset.com/course-lesson/importing-content-from-csv-with-post-relationships/#how-toolset-associations-can-be-added-to-a-csv
In summary, in your export file, you'll need to include the title of the parent post, as a value in the custom meta key in format "_toolset_associations_%relationship_slug%", with each child post.
However - I found a better way.
You will have to use native WordPress export.
What I've done is I've setup a brand new sandbox site and then I've exported the Types structure (that will export post types, taxonomies, custom fields, custom field groups) definations.
So, I've exported the Types structure from:
Toolset => Export / Import => Types tab and click on the button "Export" to export the Types structure from your site.
I've created the following sandbox site and you can auto-login to it using the following link:
- hidden link
Now, I've impoarted the Types structure that I exported from your site to the sandbox site:
=> Toolset => Export / Import => Types tab => Import Types data section and upload the file that I've exported from your site and click on the button "Review and Import".
So, all post types, custom fields, taxonomies, post relationship will be automatically created to the sandbox site.
Now, I navigate to your site, and exported:
=> Tools => Export and selected the Artist (parent) post type that will offer you XML file
=> Tools => Export and selected the Art (child) post type that will offer you XML file
To import the content to sandbox site I've created, I navigate to:
=> Tools => Import and first imported the Artist (parent) post type XML file
=> Tools => Import and first imported the Art (child) post type XML file
Then, I navigate to:
=> Toolset => Export / Import => Associations tab and you will see it will show you to associations for your post relationship and you can click finish the process by click on the button "Start Import".
Then with I check any Art post that you claim missing relations as per the following screenshot:
- https://toolset.com/wp-content/uploads/2025/09/2825339-Screenshot_2025_09_17_at_7.15.59_AM.jpg
Like:
- hidden link
- hidden link
I can see it does show related post on post edit page.