I know the question about multiple concurrent admin log-ins has come up in the past. At the time, one of the key reasons for not supporting is was the concern that multiple concurrent admin connections could wreak havoc on the configuration. Part of the argument (and rightfully so) was that since ASUS didn't support it there was probably a good reason for that.
However, ASUS now offers applications for Android and iOS that allow admins to make changes from a mobile device while another admin connection is active in a browser.
I have not examined the traffic from the mobile devices yet so I have no idea how ASUS is connecting to the router and how they are handling it, but it does seem to establish that multiple concurrent admin connections are (now?) supported.
However, ASUS now offers applications for Android and iOS that allow admins to make changes from a mobile device while another admin connection is active in a browser.
I have not examined the traffic from the mobile devices yet so I have no idea how ASUS is connecting to the router and how they are handling it, but it does seem to establish that multiple concurrent admin connections are (now?) supported.