Please describe step by sep what you are doingand what you want to do? That can help to undesand the details.
Yes. As you can see in the video I grouped some elements and then I tried to make it fixed in the vertical scroll, but if I do it both in the prototyp or in a design tab, in both cases the group disappears in the final render
They don't disappear. The element you want fixed is below the fold and is outside the viewport (the dashed line). Because it's 'fixed', when you scroll it stays in place and doesn't come up with the other elements.
I get what you want to do - you want the element to scroll up until it reaches the top of the screen, and then stay fixed, but for now you can't do that. Unfortunately, you can't limit when an object becomes fixed. You can either make it fixed in place, or make it scroll with the other elements.
Ah ok, I got it... it would be very useful 😞
I have the same problem, did you find a way to fix it?