Here’s how it works:

There’s not much of an interface for this one, you simply go to a sheet
and run the command.  It will then go into a selection mode asking you
to “Pick viewports in the desired order.”

Download Viewport Renumber 2013, 11.48 kB

Download Viewport Renumber 2014, 11.92 kB

Original post by Tim Logan:

Revit Viewport Renumber Tool | LMNts