How can I create a backup automtion to only backup Core, the DB and a small number of specified addons to nabucasa?
I can’t select that destibation in the actions page:
Assuming you have a Nabu Casa subscription (HA Cloud) and you’re currently logged in, then you don’t need an automation for this.
You can simply set your automatic backups to only back up the specified addons & db (History) and choose the Home Assistant Cloud option in your Locations.
Then, if you want a full backup saved locally, you can use an automation to trigger a full (manual) backup every x number of days/weeks.
Ref docs:
Backups tasks
Backup Integration