You can add multiple API keys to use when using username and password (API key) authentication. To do this, navigate to your Authentication page here. Next, click on the "Add New Key" button, as you see below:

Click "Confirm" when the window pops up asking you to confirm.

You will then see multiple API keys on your Authentication page, all of which can be used for authentication.

If you want to delete an API key, simply click on the red trash can icon next to the API key that you would like to remove.

Click "Confirm" when the window pops up asking you to confirm.