Due to limitations with Google Business Profile (GBP) only allowing only one page connection at a time, you cannot switch between two different GBP pages by following the "Edit Connections" workflow within Social Marketing. Attempting to do so will display the error "You can only have one GBP location connected per account."
From Social Marketing > Settings > Connect Accounts, click the "Remove" button on the GBP you would like to disconnect. Once the GBP page is disconnected, you may come back to this page and connect the new Google Business Profile page you would like to use.