Marking a heard voicemail message as "Unheard" (or other)

I'd very much like to know if Apple has some way of marking a voicemail message as "unheard" once its been listened to. I've checked the boards and have only found one item related to this.

I'm basically interested in the ability to do with voicemail, what can already be done with email (see below.... "Mark as Unread")....

or the ability to tag it so that I have a visual cue to go back and re-listen and/or address the voicemail when time allows. Is anyone aware of how this is possible, if at all? And if not, how can we get Apple to consider building something like this in (below)??