Is there really no way to access this design page?

Hello. When I first used spreadshirt to experiment as a client, I’ve gotten to this page

I liked designing with this page and assumed as a creator, you’ll be designing in a similar environment.
However, after creating the spreadshop it seems like this page is nowhere to be found and designing products is way more limited? You cant add several designs onto ONE printarea, you need to spread it over individual printareas, and not even that seems to work, since it ignores the printareas you defined and rearranges them? I tried using Design Nr 1 on the front of a shirt and Design Nr 2 on a sleeve, and when I reviewed it, the sleeves were empty but the backpiece was filled instead?

Does anyone have any idea what causes that or how we’re supposed to design in case we want something else than a picture on someones chest?