When you create an annotation, you will find recent annotations in the Suggestions list here:

This list will include recently created annotations and annotations that have been deleted from a document. Therefore, this is actually how you can ‘move’ annotations within a document:

1. Click on the annotation you want to move, and select Delete

2. Click the new place in the document you want the annotation to display

3. Click the blue annotation button that appears and select the recently deleted annotation from the Suggestions list

4. Click Save

A new annotation will be created in the new location.