@smi-jonathan global moderators exist as a group to essentially be admins but without access to the ACP. If you want a restricted group of admins, that's what you're looking for. If you'd like them to be able to do more, then I'd suggest opening as issue on Github. As for your particular request, no, this isn't possible without a plugin.
Create an account via third party app
We have a separate user management system where we want our own users to have the ability, via our admin pages, to create users on our NodeBB installation.
Essentially it's a debating club for kids, and we want the parents (or schools) to create accounts on our current system, then be able to create logins for their kids on the NodeBB installation. What would be the best way to go about this? Would it require a custom plugin?