Would love to see a feature that allows notes to be added to monitors? I believe Nagios has this feature. It would be super helpful for tracking (e.g. being able to add a ticket number to the monitor to know it is being worked on).
Old request but it happened to bubble up to the top today so I thought I would chime in. Alerts have had notes available for many years, and nodes themselves also have a notes section. Both features seem to be rarely used by most people I run into, but they are built in. This should probably be marked as implemented already.