Allow the edition of the labels/colors of the annotations
A menu entry Annotation ⇒ Edit Labels/Colors…
should be added. This action would open a panel like the following:
![bitmap](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)
where the user can click on the annotation boxes to change its label and its color.