I can only even find a couple places in the docs that suggests this is possible, but it clearly is possible.
Moving a snap between channels helps to manage a user’s expectations in any trade-off between stability in the stable channel, and cutting edge features in the edge channel (as an arbitrary example). But its also a useful technique for beta testing, or for when a snap needs to revert to a previous revision. -- https://snapcraft.io/docs/release-management
Take for example kubectl (see below) which has a channel for each old minor version, in addition to the default latest channel.
We're about to release a new version which will not be compatible with Ubuntu 16.04 and below, and we'd like to make the old version available to those users. How can we achieve that?
❯ snap info kubectl
name: kubectl
summary: Command line client for controlling a Kubernetes cluster.
publisher: Canonical✓
store-url: https://snapcraft.io/kubectl
contact: https://www.ubuntu.com/kubernetes
license: Apache-2.0
description: [...]
snap-id: ZgG2URycDgvxSVskfoZxn44uaRMw0iwe
channels:
latest/stable: 1.21.1 2021-05-14 (1976) 11MB classic
latest/candidate: 1.21.1 2021-05-14 (1976) 11MB classic
latest/beta: 1.21.1 2021-05-14 (1976) 11MB classic
latest/edge: 1.21.1 2021-05-14 (1976) 11MB classic
1.22/stable: –
1.22/candidate: –
1.22/beta: –
1.22/edge: 1.22.0-alpha.1 2021-04-29 (1945) 11MB classic
1.21/stable: 1.21.1 2021-05-13 (1976) 11MB classic
1.21/candidate: 1.21.1 2021-05-13 (1976) 11MB classic
1.21/beta: 1.21.1 2021-05-13 (1976) 11MB classic
1.21/edge: 1.21.1 2021-05-13 (1976) 11MB classic
1.20/stable: 1.20.7 2021-05-13 (1949) 9MB classic
1.20/candidate: 1.20.7 2021-05-13 (1949) 9MB classic
1.20/beta: 1.20.7 2021-05-13 (1949) 9MB classic
1.20/edge: 1.20.7 2021-05-13 (1949) 9MB classic
1.19/stable: 1.19.11 2021-05-13 (1947) 10MB classic
1.19/candidate: 1.19.11 2021-05-13 (1947) 10MB classic
1.19/beta: 1.19.11 2021-05-13 (1947) 10MB classic
1.19/edge: 1.19.11 2021-05-13 (1947) 10MB classic
1.18/stable: 1.18.19 2021-05-13 (1951) 10MB classic
1.18/candidate: 1.18.19 2021-05-13 (1951) 10MB classic
1.18/beta: 1.18.19 2021-05-13 (1951) 10MB classic
1.18/edge: 1.18.19 2021-05-13 (1951) 10MB classic
1.17/stable: 1.17.17 2021-01-15 (1777) 10MB classic
1.17/candidate: 1.17.17 2021-01-15 (1777) 10MB classic
1.17/beta: 1.17.17 2021-01-15 (1777) 10MB classic
1.17/edge: 1.17.17 2021-01-15 (1777) 10MB classic
1.16/stable: 1.16.15 2020-10-20 (1639) 10MB classic
1.16/candidate: 1.16.15 2020-10-20 (1639) 10MB classic
1.16/beta: 1.16.15 2020-10-20 (1639) 10MB classic
1.16/edge: 1.16.15 2020-10-20 (1639) 10MB classic
[...]
These are known as "Tracks". Each one has their own edge, beta, candidate, and stable channels.
There is a process that requires you to request new tracks via the forum.snapcraft.io discourse. See https://snapcraft.io/docs/process-for-aliases-auto-connections-and-tracks for more details on the procedure.