pane-border-lines-enabled <----------------
             Show pane borders.  Value may be one of: 'on', 'off'. Default: 'on'.

     pane-border-lines type
             Set the type of characters used for drawing pane borders.  type may be one of:

             single  single lines using ACS or UTF-8 characters

             double  double lines using UTF-8 characters

             heavy   heavy lines using UTF-8 characters

             simple  simple ASCII characters

             number  the pane number

             ‘double’ and ‘heavy’ will fall back to standard ACS line drawing when UTF-8 is not supported.