Since the launch of the Multi-Linking feature this past fall to help users managing multiple accounts, Bing Ads now offers an additional way to manage multiple accounts easily.

Users who have Multi-User Access will allow them to have a single email and password to access all of the Bing Ads accounts they manage.  With this single login feature, it will further streamline switching between different clients.It will even eliminate the need for multiple logins, which is great for the ease of use.

Once you login, the accounts an email has access to will be listed.

Image from Bing Ads

Accounts that are available to users can be accessed from a drop-down menu, which is available in the upper right beneath the login credentials.  Not only that, users have the ability to manage defaults and remove their access.

If you are interested in accessing the feature, and you have multiple accounts via multiple logins, you can contract Bing Ads support to have them consolidate under one login.  Another option is to accept user invitation requests to the login you with to use.

Important Note: Bing Ads API version 11 does not yet support this feature. Because of this, account access will still need to be done via the original login used.  Version 12 should help fix the problem.

Source –