Some important things to keep in mind.
All API keys are stored separately using the password you enter on the login screen (If you skip using a password it will still be encrypted but with a randomly picked value in the background).
In order to instantly switch between multiple API keys at the same time you'll need to continue using the same password. It is perfectly fine to use multiple passwords if you do not want this to be possible.
If you do NOT log in with the same password, the keys which used a different password will not be select-able in the menu until you log out and log in with their password.
Now to get started:
- Log out of your account. This is possible on the dashboard by clicking the small Logout icon at the top right AND the login screen by clicking the
Marked with red on the right in this screenshot:
Enter the same password if you want to quickly switch accounts or use a different password if you want to keep them separate.
Log in to your other account, this can be a regular or OAuth API key.
From that point on, after you enter a password you will see a button at the top right of the API login screen.
And when you are on the dashboard there will be a small Key icon on the dashboard at the top right. Marked with blue on the left in this screenshot: