What functionality is missing? What is unsatisfying with the current situation?

At present I am running a campaign and at the same time writing for a different world I am creating. I constantly have tabs open of pages I am working on but always have to change between worlds if I need to plan for my next session. This has the unfortunate effect that pages I have open for the world I was on stop working if I forget to switch the world back. When I save the results are inconsistent and all links/pages/menus change to the world you have selected. It would be nice if you could open a world into an instance and that world and any pages you open in tabs in that instance are able to exist without issue. A new instance you can then have another world open that could can work on simultaneously.  

How does this feature request address the current situation?

Allowing the sessions to exist within a browser instance you could open different worlds and edit them simultaneously without having to switch between worlds.  

What are other uses for this feature request?

This could make it easy to copy information or pages from one world to another without having to export/import pages or use text editors to copy the info across.