Annotation marker is not keyboard accessible

It's possible to create annotation with a keyboard only (even without a screen reader), but it's not possible to access the annotation "menu" through the annotation marker (post-it in the content). At the very least, this should be accessible using a keyboard. At best, the bubble it opens should look like it respects tab order (right now, the bubble is semantically at the very end of all content and not in the middle like the way it looks).