Hello Clara!
We have done a lot of work to improve our portfolio in the latest version of the theme (1.4.5).
But unfortunately, we didn’t implement that option yet.
Anyway, I think I found a simple solution to solve your “Problem”:
Just go to Vision Portfolio->All items, then edit the desired item and on the top-right side of the item page, edit your item publishing date…
https://prnt.sc/kcngm4
By the changing the date of the publishing, you can reorder your portfolio items on the way you want.
Hope this helps you to solve your “problem” for now.
Regards