@extua are you aware of lifecycle prefixes?

https://wiki.openstreetmap.org/wiki/Lifecycle_prefix

there's a street_vendor=yes tag that I've used for kebab vans that appear every evening, and also an impromptu tag which I've just seen on the wiki

https://wiki.openstreetmap.org/wiki/Tag:street%20vendor=yes?uselang=en-GB

https://wiki.openstreetmap.org/wiki/Key:impromptu