Put time marks on Graphs, suggesting changes on monitored Host.

Hello to all.
I'm thinking about a way to add a mark for marking some type of significant change on a monitored host. Explaining better, this would function as a Easy view for new behaviors, after a change like: after i have placed 2 more virtual hosts in a web server, how much is consumed my resources?
This can be done with the keys like "vm.memory.size[]" but need other approach envolving Trigger and etc.

I'm suggesting that a "Graph" element could have an item that be placed (configured to appear and disappear) as a time mark, linked to a history time (a point on time) informing in that point had a change in the Server, and could be manually informed by one of the netadmins.

Annexed image have as exemple. Please see the last item.

Best Regards.