Wilder-Kaiser-B-V-Pink-Puma In the app you can select profile (on the bottom right). Then on the top right there is an icon with two people. Click on that an you get a page for all the accounts on the phone and a big plus sign which you can use to create a new Business bunq accounts.
Once you have multiple accounts on your phone you can use a long press on the profile icon to switch to another account more easily.
You can also connect any of your joint BV bank accounts to your own BV account. Then you can control that account even when you are logged in on your own BV account.