For information, the node-red-contrib-google-smarthome node is likely to be updated shortly.
Currently, the node credentials are saved in the flow itself (which are exposed if you export a flow), and the change will ensure that the credentials will be in future safely stored in node-RED's
flows_cred.json encrypted file instead.
This is likely to be a breaking change, as when updated, you will need to re-add your credentials again.
I found it useful in preparation for this change, to highlight the
Smarthome Management node and export it. The result will contain the Client ID, Client Secret, JWT key, etc, which can then be easily pasted back when you have updated.