Initialize a class (HX711) within a class with constructor and parameters
Unfortunatly HX711 has no default constructor. So the easiest way would be to add one in the header:

HX711() {} // default constructor, empty


Add member function to do the init job (done by original constructor), also in the header file

    void Init(byte dout, byte pd_sck, byte gain = 128) {
    PD_SCK  = pd_sck;
    DOUT    = dout;

    pinMode(PD_SCK, OUTPUT);
    pinMode(DOUT, INPUT);

    set_gain(gain);
}


Now your ScaleMeasure class will be like (header):

class ScaleMeasure
{
 public:
    ScaleMeasure(int Dout, int Clk, float CalibF, int ScaleID); 
    void Setup();   
    float Measure();    

private:
    int _dout_pin;
    int _clk_pin;
    float _calibration_factor;
    byte _scaleID;
    HX711 _scale;  
};


and cpp

ScaleMeasure::ScaleMeasure(int Dout, int Clk, float CalibF, int ScaleID)
{
    _clk_pin = Clk;
    _dout_pin = Dout;

    _scale.Init(_dout_pin, _clk_pin);  

    _calibration_factor = CalibF;
    _scaleID = ScaleID;     
}