##Setup Needs a Named Credential with scope https://www.googleapis.com/auth/spreadsheets
Settting up a Google Project and the settings on the Salesforce side of things is described here: https://unofficialsf.com/using-google-data-in-flows-authenticating-to-google-from-salesforce/ The only difference is the scope needed. ( https://www.googleapis.com/auth/spreadsheets )
Note: this version wil do 'one call' to transfer all values so there is probably a limit as to how many rows it will succesfully handle. Probably the 6mb heaplimit will be hit before the Google Sheets limit. Will be a nice to have for a next version to be able to give a number of rows to be updated at once.