it would be great to make a mark at the Timeline, that would shown at all reports. So you can see the effects of your promotion and mailing in every report.
If you are interested in this feature please get in touch for a donation! we are hoping to work on it very soon (contact at matt@piwik.org for more info if you wish to crowd fund this feature of annotations)
Thanks for the information,
Annotations seems to be the correct name
killer feature!