It is noted here and in the help that you can set "run as".
/RU username Specifies the "run as" user account (user context)
under which the task runs. For the system account,
valid values are "", "NT AUTHORITY\SYSTEM"
or "SYSTEM".
From my tests these commands will start the task
schtasks /create /sc once /st 00:00 /f /tr foo.exe /tn bar
schtasks /run /i /tn bar
However running it as SYSTEM will not launch foo.exe
schtasks /create /sc once /st 00:00 /f /tr foo.exe /tn bar /ru SYSTEM
schtasks /run /i /tn bar
The reason I would like to run as SYSTEM is because it was said in the other question that doing so would essentially run foo.exe
in the background without a window.