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tickbox variable: $all3flag -- toggle 1 <-> 3 views
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keyboard equiv: <none>

The "all3views" tickbox toggles state of display
between 1 fullsize view and smaller views of all
3 planes plus max view.  (CORONAL->upper left,
HORIZONTAL->upper right SAGITTAL->lower left).

Clicking in one view updates the 2 other views
and changes the focus of the arrows keys to the
clicked plane.

Clicking anywhere in maximum intensity projection
view (lower right) returns other 3 views to
center.  OK to edit any plane in this state.

