I suggest a new feature to allow cancelling scheduled downtime once it has started. The documentation states: "When an scheduled downtime is "working", it couldn't be neither modified nor deleted. " I verified this statement is currently accurate. There are two scenarios that this new feature is useful.
1. The scheduled downtime activities complete early. That is, instead of taking 8 hours, only 2 hours were needed.
2. The scheduled downtime is accidentally entered for a large time span. For instance, instead of for 8 hours, you enter the date resulting in 1 year and 8 hours. There is no way to end this scheduled downtime, it seems.
The consequence is no network management monitoring or editing of the selected agents is allowed/provided until the downtime ends, possibly a year later! (In my case, I accidentally set it for an extra day later.)