Hi Gil thanks for posting in the community! You are correct that if you go under the "Attached Images" section under the menu on the very right hand side of the formatting bar. I have attached below a screenshot of this section.
If you reorder the images there the order you put them in should be represented when you click off and back into the shape. If that is not the case can you please submit a ticket using our Contact Support Form and provide a screen recording and your doc URL so we can take a closer look?
For anyone else using our Attached Images feature please check out this Attach Images article for additional information.