How to create an admin account from non-admin privileges

You want to perform an administrative task without administrator credentials...

That's not possible.

No, it is not possible to create an administrator account from a non-administrator account.

Doing so would effectively constitute a privilege escalation attack, which is something that is generally taken very seriously by software vendors as it makes any attempts at privilege separation of users moot; the user (or code running as a user) could just create a higher-privileged account and switch to using that instead, bypassing any protections in place. Particularly if it can possibly lead to local administrator access, many access controls can be bypassed relatively easily once such access has been obtained.

In general, privilege escalation attacks is the class of attacks where you start out at some privilege level, perform some (set of) actions, and end up with higher privileges without actually involving some entity (most often physical person and/or user account) that actually has the privileges you obtain, which would normally be needed in order to elevate the account to the higher privilege level.

A basic design criteria for a working privilege system is that no entity can elevate itself above the entity's own original privileges. Many computer-based privilege systems also include a requirement for being able to reduce privileges, after which raising the privileges back to the original level should not be possible. This is generally referred to as dropping privileges.