The 2015 Mk7 GTI that I am driving is pre-owned and arrived with a set of ST coilovers already installed.
I had planned to adjust the coilover height eventually, and inspection of the front tires prompted taking action sooner rather than later. Moderate undulations on a highway could produce wheel rub with the fender.
Raising the front end was straightforward with the coilover adjustment collar easily accessible. The rear was a good bit more of a pain. The part shown below is for making the height adjustment.
The image shows the adjuster after raising the rear. When starting the two parts shown by the yellow arrows were together. Turning the lower ring while not turning the inner barrel is not a trivial matter. The top half is not fixed to the underbody and will turn with the lower ring. Size and location make holding the one part fixed while putting a spanner wrench on the other a tricky proposition.
To accomplish this task first a set of channel locks pliers were used to hold the barrel by the threads, not the most desirable way to go about it but there are limited options. Once the notched ring is far enough from the smooth upper disk an oil filter wrench was used to hold the top in place while turning the notched ring. Figuring out the right tools and way to get this adjustment made, and getting both rear coilovers set, was several hours of effort.
The ride height was determined by measuring the fender to wheel center. At the front the car measures 13.25″ and the rear is 14″. After a few days of driving this will be checked again to determine if any further adjustment is needed.