I logged as root
click : administration options > switch to server admin > access server admin
in server admin : cannot find the way to switch back to admin
I have learnt directadmin will have the similar feature, when logout from user, will auto switch back to reseller or admin level
so, when I logout from virtual admin in server admin, will logout, need to login root account again.
not critical problem, but, sound that can be better on this.