When I originally folded Parallelograms in 2020, I designed a clean pre-crease pattern, pre-creased the sheet, and then… was unable to collapse it cleanly. I went back to folding the model from a complete grid, but kept the original precreased sheet for later. That time came in 2022 when I revisited that sheet, and with more folding experience under my belt, was able to collapse it neatly this time. You can see slight creases on the parallelograms’ surface, but they are not very conspicuous, and would probably not have appeared if I had used paper with better bendability than Tant or even just placed the precrease pattern on the sheet rotated 90° in order to make better use of paper grain.
Some designs take a lot of time to fully develop, and this one is quite typical: