Hi @danny, welcome to the forums!
Yeah, some of those aspects need more polis user experience wise, but will try to clear it up a bit:
The move between deployments happen using the os-config join command inside balenaOS. You can check the command by logging into the device, and running os-config --help and os-config join --help
To move between balena installations, you can get a config.json file from your target installation, make sure it’s a single line (it will be, downloaded from balenaCloud for example the “Add Device”/“Advanced”/“Download configuration file only” step), and run the command with os-config join '{configjsoncontents....}' such as os-config join '{"applicationName":"....}'
For example like this, when I was connected to the device:
The balena join works on development version of the OS only. That does the preconfiguration for you, and underneath also using os-config inside the device (and generating the config.json as needed). If you device is a dev version, then you can use that, and just log into the balena installation that you want to move the device to, and balena join <deviceip> will give you the list of applications where you can move the device to.
Here moving a device:
There’s also this other thread from earlier, which might have some extra info for you too: Is possible to move from Balena Cloud to Open Balena?
The reverse process would be the same with providing config.json / logging in with the CLI to the new target installation.
Hope this helps!