When switching schedules from one group to another, particularly when taking small routes away to add LH 7-day stuff, you end up with a lot of owned, unused slots at destination airports. If you don't make notes beforehand, there's no way to find them again except looking at every possible airport, or waiting a month for the warnings. If you don't want to use them, you end up with a lot of messages about 'airport slot warning'. The ability to show a list of owned but unused slots, the same one that appears in the slot warnings, would be nice.
The ability to abandon those slots immediately would also be nice. I think a workaround for that may actually be possible now, if you create a route to the airport, use the free destination slots, and check the box to not buy HQ slots. Then cancel the route and release the slots. Haven't tested it though.