How can I use master realm admin credentials to manage users in another realms

In the keycloak UI I can jump in any realm with my master realm admin credentials and create/modify/delete users as well as manage realm config.

However when I’m trying to do the same from API, user modifications are failing, at the same modifications to config of other realms work…

Could you please give me a hint, how I can use master realm admin to manage users in other realms?
A few important details:

  1. I’ve seen some recommendations to assign “realm management” privilege in target realm for the master realm admin user, however I cannot find this user in non-master realm user list
  2. This approach doesn’t really work for us, because we have a lot of realms, also many of them created dynamically, so I would rather try to achieve the same behavior I have in Keycloak UI, where master realm admin has effectively god power and can do anything in any realm.

Thank you in advance!