For the variables thing, I will do that later, because this requires some additional checks. The issue here is that we can use Constant or Variable in different ways, not only by right-click and select.
Areas. I was thinking about this before, but the problem here is what happens when you collapse or expand an area, because there can be other blocks around - what happens with them? Especially when you expand.
I think I prefer to make something like pagination, to be able to put some blocks in page 1, other blocks in page 2 and so on.