// /src/Mod/Sketcher/App/SketchObject.cpp
// ...
// line 73
include <Base/Parameter.h> // add
// ...
// line 724
int SketchObject::toggleConstruction(int GeoId)
{
    const std::vector< Part::Geometry * > &vals = getInternalGeometry();
    if (GeoId < 0 || GeoId >= int(vals.size()))
        return -1;

    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/Mod/Sketcher"); //add
    ParameterGrp::handle hSubGrp = hGrp->GetGroup("General"); // add
    bool allowcp = hSubGrp->GetBool("AllowConstructionPoints", false); // add
    if((vals[GeoId]->getTypeId() == Part::GeomPoint::getClassTypeId()) && (!allowcp) ) // edit
        return -1;

    std::vector< Part::Geometry * > newVals(vals);

    Part::Geometry *geoNew = newVals[GeoId]->clone();
    geoNew->Construction = !geoNew->Construction;
    newVals[GeoId]=geoNew;

    this->Geometry.setValues(newVals);
    //this->Constraints.acceptGeometry(getCompleteGeometry()); <= This is not necessary for a toggle. Reducing redundant solving. Abdullah
    solverNeedsUpdate=true;
    return 0;
}
// ...