This took me quite awhile to find so I wanted to share this with other people.
To switch windows in vimdiff or
to navigate windows in vimdiff or
to change windows in vimdiff try the following:
The ":vertical" command can be inserted before another command that
splits a window.
MOVING BETWEEN WINDOWS
CTRL-W h move to the window on the left
CTRL-W j move to the window below
CTRL-W k move to the window above
CTRL-W l move to the window on the right
CTRL-W t move to the TOP window
CTRL-W b move to the BOTTOM window
Moving windows
=====
CTRL-W K move window to the upper
CTRL-W H move window to the far left
CTRL-W J move window to the bottom
CTRL-W L move window to the far right
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I post this info because I has so much trouble finding it.
vimdiff - Edit two or Three versions of a file with Vim and show differences