How to watch all FormControls ValueChanges except specific control?

You can merge individual valueChanges Observables into one like so :

Observable.merge(
    [ control1.valueChanges,
      control2.valueChanges ]
  ).subscribe(() => {
    // do your computation
  });

Is there a reason why you couldn’t create a FormArray instead of multiple form controls? For example

form_group = this.fb.group({
    'controls': this.fb.array([...])
});

Then you can define a property in your component

get controls(): FormArray {
    return <FormArray>this.form_group.get('control');
}

And then from this you can iterate the form array and subscribe to valueChanges

this.controls.controls.forEach(control => {
    control.valueChanges.subscribe(...)
});

You can then apply some logic in the for each to exclude the controls you do not want to subscribe to

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