In case anyone is interested, here's my modified behavior shown...
https://youtu.be/lJtoyFGpZVY

And here's the code patch...
- Intersecting rooms and walls are guides
- "other" layer content is not editable.
I don't see a way of uploading files, so sharing via a cloud service.

sweethome3d ...

Thanks for the reply
I'm just saying that I quickly became frustrated with the behavior because I did not understand it ("other layers" being guides (or not) or being editable (or not) or visible (or not) in the plan view). So much so, I felt the need to get the source code to understand "why".

It ...

I have a further understanding of the code behavior related to the plan view, but still learning.

The code/rules are obtuse and inconsistent (IMO).

paintOtherLevels: paints the "reference" (shaded/hidden walls)
- If at "level0" (the magic "first level created"..."level0" does NOT have to be ...

I've downloaded the source and trying to understand by debugging the code.
It appears the behavior I'm describing is contained within the "paintOtherLevels" method of the PlanComponent.
Unfortunately I'm not a native Java speaker, so it's taking me more than a few moments to grok it, but I'm ...

I'm running 6.4.2 currently.

I've read everything I can find, but the behavior does not make sense to me.
If I create a new layout, add a couple walls at "level 0", then create a "new level" (level 1), the prior level walls are shown as "hidden" (guides)...If I raise the height of first levels ...