Try this one: https://bugs.launchpad.net/snapstore/+bug/1771148 which would actually be a nice place if you need to describe your use case
You can close the channel. Example:
snapcraft release firefox 87 esr/stable
all looks OK, then:
snapcraft close esr/stable
esr/stable gets closed and the snap becomes unavailable from there.
esr syntax alone should work, I tested with a track I have and
esr in this context should be equivalent to