This has come up in the past, you are correct a single User account cannot be assigned to multiple levels. There are two work arounds, as you said create multiple user accounts with different e-mail addresses and login with each different account for the specific level you need to access, or have full top level privileges to your whole groups TT account. That is the easiest way to do it however not everyone likes the idea of having so many with top level access to everyone. Do a search for leader in multiple Dens, Patrols, Units and add you support of the feature to allow a user to be assigned into multiple levels.