Permissions user by user for managers features

I have a question about how users work and their permissions. I need the master admin to create managers for each company so they can register new limited devices, manage maintenance and geofences, and not see all users on the platform (only their own users). I was only able to do this by setting them as admin.

I need to create users who can create their own virtual fences/manage notifications/maintenance, but who cannot see all users on the platform.

I couldn't find a permission for this.

Does this not exist or am I doing something wrong?

You're probably looking for the manager role. Please carefully read this page:

https://www.traccar.org/user-management/

I read this documentation but it wasn't clear how to set a user as a manager. Could you help me understand?

In the options, there is only one marker for "Admin" and the rest of the settings are based on the limitations of a client.

You have to set user limit to something other than 0. The documentation is pretty clear about it.