Open " qgroundcontrol [Stable_V4.0] " Then " Reources " , which is below Sources ( which is with c++ extension & sign ) Then " qgroundcontrol.qrc " Then folder with name " /toolbar " , which below " /qml " Now double-click on " MainToolBar.qml " - now you are ready to edit the code , ,,, - navigate to last " QGCToolBarButton " - now goto it's close tag . ...