gtk:tree-view-expander-column (object)

object -- a gtk:tree-view widget
column -- a gtk:tree-view-column object for the column to draw the expander arrow at, or nil

Accessor of the expander-column slot of the gtk:tree-view class. The gtk:tree-view-expander-column function returns the column that is the current expander column. The (setf gtk:tree-view-expander-column) function sets the column to draw the expander arrow at. It must be in the tree view. If the column argument is nil, then the expander arrow is always at the first visible column.

If you do not want expander arrow to appear in your tree, set the expander column to a hidden column.