Thank you for the explanations.

1. Memory
I was programming in NI LabVIEW and for the last 10 years in C# for the .Net Framework. Both running on Windows. In both environments the garbage collector will decrease memory when the new loaded file needs less objects than the old one.
I never programmed in Java so I don't have any experience with it. But I expected when starting SH3D the memory is b. Loading Home1 it is b + h1. Loading Home2 giving a second instance of SH3D it is b + h1 + h2. Removing the instance of Home 1 it will give b + h2 + r. I think r is management information for the objects which is also be used by Home 2.

2. 3D View
I was always asking myself how I can close the 3D View. I see the three dots on the three splitter bars (the vertical one and the two horizontal). But I don't see an arrow even not in GIMP with 400 % scaling.