c_gtk_tool_item_set_proxy_menu_item

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
__gshared extern (C)
void function(GtkToolItem* toolItem, const(char)* menuItemId, GtkWidget* menuItem) c_gtk_tool_item_set_proxy_menu_item;

Meta