Method 1

Step 1. Open sequence and annotations in Sequence view

Note, that sequence and annotation table can be located in different files.
In this case just drag-n-drop annotations table object to the opened sequence view.

Step 2: Ensure that the file with annotation table object is editable (no lock sign in the icon). Read more to learn more about this here

Step 3: Select an annotation in the annotation editor and press F2 key to rename it.