Could you clarify what you mean by:
vs
You make it sound as if there were 2 editors, while there is only one - the Designer
Could it be you’re referring to the brand new widget preview feature?
Besides that, note that how widgets behave is dictated by their parent. If I work in a lone user widget:
This progress bar seems like it’s going to take the entire screen - this is just a preview, not the final result. The final result will become more clear once I add this widget to another container - then we need to consider what that container is sitting inside of… this whole thing trickles down and revolves around Desired Size which children can report and parents can, optionally, respect or ignore via alignment settings of the slots they produce.