I used to carry out an engine flush on my VW Group cars every year after they had reached maybe 6 years old so maybe from 40K miles onwards, but I only ever used Comma Petrol Flush which can safely be left in the engine's oil for roughly 100miles/7days - though I'm not sure what extra benefit it did,
I've always changed engine oil every 12months/8K miles(roughly) and used what should be considered good/premium oils.
For our current VW Group cars, I've not done that, dealerships did always seem quite keen to include an engine flusher dose in the service price though - what ever that means other than a bit of "upselling".
So, my advice is to just start adding a bottle of Comma Petrol Flush, if it still states that it can be left in the engine's oil system for a week's worth of running, a week before carrying out an oil change - or, if the service history shows that that car has had "good/premium" oil in it and replaced at the correct intervals from the start of its life, just add a flusher once every other year - or even not at all. (sorry a flippy floppy answer!)
Edit:- my VW dealer, cautioned me over me jumping in early and changing the oil in my 2000 VW Passat 4Motion during its first year of life! Their reason being "VW Group have had the approved engine oils designed so that they act as normal oils for the first 9 or 10 miles/ 4500 or 5000miles of use, then the oil changes its chemical structure to turn into a scrubber and clean out all the engine's internals" - this was backed up by the workshop top tech, I kept my cool and suggested that I could actually sell them the removed oil as it must now be in its prime, just ready to clean out an engine, they were not impressed.