By default, TimeSheet works on local Tag timeline. Once ManicTime is connected to a server, you can run TimeSheet on any server Tag timeline to which you have access to.
Once you are connected to a server, ManicTime will show all Tag timelines you have access to. You can choose as many tag timelines as you like to make a timesheet. ManicTime will pull data from all of them and combine it into a single report.

For this to work you only need a server connection, you don't have to add timelines to the Day view, ManicTime will list all Tag timelines it finds on the server regardless whether they are added on Day view or not.