As a user of the New User Experience, I want to have the ability to have more than one Page or Worksheet open at a time.
Depending on the setup of a model, and UX, many users may create temporary views and jump back and forth between a couple of grids to validate or compare. In the classic UX, you can have multiple Dashboards open and even pop one of them out to view them side by side. Right now, the only way that I am aware of in the New UX is to have multiple browsers tabs open, in which case synchronization does not work.
I know this is successful when I can have multiple Pages or Worksheets available as tabs at the top of the interface, similar to the Classic UX.