First off, I wouldn’t use the word “Panel” to describe what you
want, since an “NSPanel” is a kind of “NSWindow”. Let’s call them
Second, I wouldn’t use an NSTableView to contain your panes.
NSTableView really isn’t designed for that, it’s for tabular data. You
can use an NSStackView, which IS designed for it, or just use raw
constraints and autolayout, manually setting the top of each pane to equal
the bottom of the previous one.