Any experience returning items from multiple orders together?

Hi so I have recently made like 4 separate orders with a lot of items in each and I will have returns from each order because I got a few articles in different sizes to try.

I saw on the website they say returns from multiple orders shouldnt be sent together so they dont have problems processing things but I‘d gladly avoid paying the 6 eur shipping 4x…

Has anyone done it successfully? I was thinking I could put the items from each order together in a separate bag inside of the box then there’s really no difference from sending individual boxes right? 😅

I hope it makes sense what I’m saying (and I know I sound cheap but no one likes paying for shipping ok)