Gtk.TreeView.prototype.set_show_expanders

function set_show_expanders(enabled:Boolean):void {
    // Gjs wrapper for gtk_tree_view_set_show_expanders()
}

Sets whether to draw and enable expanders and indent child rows in tree_view. When disabled there will be no expanders visible in trees and there will be no way to expand and collapse rows by default. Also note that hiding the expanders will disable the default indentation. You can set a custom indentation in this case using Gtk.TreeView.prototype.set_level_indentation. This does not have any visible effects for lists.

Since 2.12