For example, I would like to make it so when the box that says “launcher” is collapsed, the box that says “Example” moves down to fill the same space that the launcher box originally filled rather than all uncollapsed elements getting stretched to fill the new space as they have been in this image. The only way I can think to do it will be to have an additional equal sized invisible box that uncollapses at the same time to fill the space above to maintain the sizing of everything but that seems like its overcomplicating the process.
Make the vertical box normally but anchor the parent container to the bottom and it will work. Add a parent container if it has none.