Thanks for posting in the Community, @yoav. I'd be happy to lend a hand with changing the master admin (MMA).
Here's how the master admin can transfer the role to an existing company admin in QuickBooks Online (QBO):
- Click the Gear icon.
- Select Manage Users.
- Click the drop-down arrow in the Action column and choose Make master admin.
- Select Make master admin on the prompt.
- An invitation email will then be sent to the user to accept the role.
For additional information on this process, I recommend the following article: Change your QuickBooks Online master administrator.
Should you have additional questions about managing users or anything topic, I'm just a post away. Hope you have a wonderful day.