I have a custom list/record field on a custom record. The list is Subsidiary. I have a checkbox field on the subsidiary that I'd like to use to filter the results of the custom field. So I have a Filter Using on the custom list/record field that looks like this, but it's not working. Am I missing something?

you're not missing anything. I have that exact setup (list/record > subsidiary field on custom record, filtering using custom checkbox on subsidiary record), and it's working:

Ok, thank you very much. Thought I was taking crazy pills! I opened a case with NS support.