How do I implement a custom divider in NSSplitViewController?

Question

I'm trying to implement a custom divider in an NSSplitViewController subclass. I want something similar to what Xcode has between the code editing area and the console area.

Ideally, I'd like to use SwiftUI for the internals of the divider itself.

I tried subclassing NSSplitView and overriding its dividerThickness property. That worked. What I can't figure out is how to actually use a custom view for the divider contents itself.

I'm looking at drawDivider(in rect: NSRect) which gives me an NSRect to work with, but I'm not sure if I can use the rect to "draw" a custom view.

I also tried this:

class FooController: NSSplitViewController {
    override func loadView() {
        splitView.arrangesAllSubviews = false
        //...
        splitView.addArrangedSubview(dividerView)
        super.loadView()
    }
}

But that results in an exception: A SplitView managed by a SplitViewController cannot have its arranged views modified.

What am I doing wrong? Am I on the right path? Should I even be subclassing NSSplitView? Or am I supposed to subclass NSSplitViewController? Or both? Or am I supposed to completely bypass NSSplitViewController and just use NSSplitView directly? Or what?