Staff members who are also parents of a student, are able to link their Playground accounts. Linking accounts allows them to use the same email and password for both the staff and parent side of the apps.
If the individual is already added as a staff or parent, make sure they've created their account with the email sent to them.
When adding the individual as another user in your dashboard, be sure to use the exact same email address in order for the accounts to link. They will receive an email like the one pictured below where they will link to their existing Playground account.
Once all accounts are set up, you'll be using the "Switch accounts" functionality to toggle between the users. Refer to THIS article to see how to switch between accounts.