My hub (C-7 running latest firmware version) setup has a "Christmas Automations" virtual switch, which over the years I've built into various rules/triggers to specify whether special handling is needed for some devices.
Unsurprisingly I've just turned that on, and as a housekeeping check went through items in the device's "In Use By" list to make sure everything's as it should be. This is the list:
...and several items are in there for no reason I can fathom. For example, "End Night Mode" in its entirety is:
The “Christmas Automations” switch was most likely apart of the “End Night Mode” automation at one time. Typically cloning the automation will ask you to remap the devices in the automation which should allow you to clean that entry up.
You need to also look on the actions page, you will find a section called "Manage Conditions", you might have an old condition in there that is no longer used (marked as unused like in the screenshots below) but still in the list. Click on the box and you will be able to delete unused conditions on the next screen.
Thanks to you both for the suggestions - checking what's in the rules it did turn out to be an old unused condition that was referencing the Christmas Automations switch; delete this, and the app vanished off the switch's "In Use By" list.
FWIW the clone option did allow an alternative to the Christmas Automations switch to be chosen, but there was no immediately obvious option for dropping it entirely...presumably if chosen the alternative would have been swapped in on the unused condition.
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