We have Process Hacker and other utilities that allows us to launch processes in interactive mode with system security principals as their user for elevated permissions. But, is there a way to log in as TrustedInstaller or other system security principal such as NT AUTHORITY/SYSTEM in a Windows 10 environment, with a full interactive GUI session? Mainly for the sake of doing dumb things in a VM.
Short answer is no, you cannot login interactively with that account as its managed by the OS and there is no traditional password associated with it.
A good reference which has in depth detail about the system account among other things is the ‘Windows Internals’ book by Mark Russinovich.