What I did: created a shortcut that creates an agenda note, then creates a things task, then uses the “append to note” url command to append the things id link to the Agenda note.
What happened: instead of appending the id to the Agenda note, it was prepended. In other words, the new text was the first line of the note instead of the last line.
Things that might be helpful to know (Agenda version, OS and model, etc): 9 b96. iPadOS 13.2. IPad Pro