After a recent cross-grade to LRT4-Pro, I have been playing around with the program to understand the new workflow. Then I was tweaking the sequence, mostly doing Ken Burns movements on a 4000+ sequence with moving boats.
Each time I changed the movements, changing 5-star keyframes, either in LRT or LR (and correctly saving and reading/reloading the metadata), the DNG-converter starts regenerating new previews.
This also happens when I go back in the process to change something else. Here I do not follow the simple linear path as described in the workflows, but go back a little. Tweaking, you know.
Generating DNG's takes each time a very long time. Is it necessary because of being able to see the new sequence in the preview window? Can this process be stopped, if is is not immediately necessary for the preview?

Just turn off the visual previews, then they won't get created. You usually only turn on the visual previews, when you're finished editing and want to deflicker. There is no point in having them turned on all the time.

Thanks for your quick reply. I did not notice, due to the slight difference in shading of the colour of the virtual button, that it was turned on.
Would that be a suggestion, to have more contrast in the on- and the off-position?

WIth a bit of practice next time you will notice :-) The Visual Previews have the pink curve and above the preview is a small Eye Button that will be selected, if they are on too.