How to retrieve/query composition association data

Hi guys,

I have requirement to query retrieve data from appointments Follow-Up table. What I see in UI designer Follow-Up data list is mapped to composition association

By structure I see that actually it is BusinessTransactionDocumentReference association, but in Apportunity's TI there is no query or other visible configuration how these following records are filtred out.

That why I have question - how can I access in my PDI coding to this FollowUp association so I could grab UUIDs and retrieve these appointments?

Thanks,

Uldis