Allow the indicator in tree mode to be customized by two new options:

tree-mode-preview-format and tree-mode-preview-style.

tmux.1

@@ -5146,17 +5146,6 @@ section.
 .It Ic copy\-mode\-position\-format Ar format
 Format of the position indicator in copy mode.
 .Pp
-.It Xo Ic mode\-keys
-.Op Ic vi | emacs
-.Xc
-Use vi or emacs-style key bindings in copy mode.
-The default is emacs, unless
-.Ev VISUAL
-or
-.Ev EDITOR
-contains
-.Ql vi .
-.Pp
 .It Ic copy\-mode\-position\-style Ar style
 Set the style of the position indicator in copy mode.
 For how to specify
@@ -5219,6 +5208,17 @@ and
 .Ic hybrid ,
 they use absolute line numbers.
 .Pp
+.It Xo Ic mode\-keys
+.Op Ic vi | emacs
+.Xc
+Use vi or emacs-style key bindings in copy mode.
+The default is emacs, unless
+.Ev VISUAL
+or
+.Ev EDITOR
+contains
+.Ql vi .
+.Pp
 .It Ic mode\-style Ar style
 Set window modes style.
 For how to specify
@@ -5463,6 +5463,17 @@ A value of 0 (the default) means no limit.
 When a limit is set, panes are arranged to not exceed this number of columns,
 with additional panes stacked in extra rows.
 .Pp
+.It Ic tree\-mode\-preview\-format Ar format
+Format of the preview indicator in tree mode.
+.Pp
+.It Ic tree\-mode\-preview\-style Ar style
+Set the style of the preview indicator in tree mode.
+For how to specify
+.Ar style ,
+see the
+.Sx STYLES
+section.
+.Pp
 .It Ic window\-status\-activity\-style Ar style
 Set status line style for windows with an activity alert.
 For how to specify