I do some calculations within my survey that result in many decimal digits. I need to keep the correct number for the further calculations but I would like to show only e.g. 3 decimal digits in the form. Is that somehow possible without creating additional "fake" fields?
Decimal questions don't have options to provide formatting while retaining values. As you indicated, the way you do this is to have a note question refer to the real value (which presumably would be a hidden or calculate question) that uses the round() function to display. One thing that may help is that if a note question is not given a name, a field will not be created for it (so no 'fake' field).