I am able to successfully apply & save custom metadata values within my Author - Assets area. I have also implemented the Custom Search Facet functionality that is outlined in the following article, which I have been able to get working as expected in the Author - Assets area.
However, when I publish an asset with a value entered into a custom metadata field to our Brand Portal, the custom metadata field & value(s) that are visible in our Author - Assets area are not showing up in the asset properties on Brand Portal.
Please see attached screenshots. Any ideas on what needs to happen beyond what I've outlined above to get this working as expected?
Once that change was made, we were able to get our custom metadata and corresponding custom search facets to publish to Brand Portal as expected. I'm not sure if that will help in your case but that's the breakthrough solution on our end.