If you have more than one GQueues account, you can access all of them from the mobile app.

To add another account choose Accounts... from the left side menu.

Then tap the Add Account button.

Login with the credentials for the other account.

To switch between accounts choose Accounts... from the dropdown menu and then tap the account you want from the list.

Choose Accounts... from the left side menu.

Long-tap the specific account and the popup menu will appear. To remove the account from the app choose Remove Account.