What I did:
Created a note in Agenda.
Added a new event to Calendar from within Agenda.
Linked the event to the note.
Moved the event within the Calendar app to another day.
Event appears in the Calendar app.
Note linked to the Event within Agenda.
After moving the event the link between the note and event was lost.
What I expected:
That the event and note remain connected / linked when updating an event in Calendar app.
Things that might be helpful to know (Agenda version, OS and model, etc):
ipadOS on iPad Pro