Accessing multiple TM1 servers from TM1 Web
When you log in, TM1 Web displays the Navigation pane for the primary server that you selected on the login screen. However, if your user name and password combination matches other TM1 Servers registered under the same TM1 Admin Server, then TM1 Web will automatically log you in to these other servers on an as-needed basis. This behavior is different from TM1 Architect and TM1 Perspectives where you have to log into other TM1 Servers as a separate, manual step.
Multi-database support mainly applies to Websheets because they can contain TM1 formulas and references that point to other TM1 Servers. For example, if you open a Websheet that does contain TM1 references to another server registered under the same Admin Server, TM1 Web will attempt to log you into this other server using your current user name and password.