If you have multiple merchant accounts, you can add all of them to one login and can be managed together from within Payments Insider.
Step 1 - From the dashboard navigation pane select Account -> Business.
Step 2 - The Business location page displays, Click on add new location
Step 3 - Add new location pop up window displays. Enter the Merchant ID (MID), and last 4 digits of bank account associated with this location.
Step 4 - Type name for new location group in text box displayed