https://stackoverflow.com/questions/63043081/nstableview-selected-row-flickering-while-scrolling-with-arrow-keys

ViewController.swift

class ClipView: NSClipView {
    var isScrollAnimationEnabled: Bool = true
    
    override func scroll(to newOrigin: NSPoint) {
        if isScrollAnimationEnabled {
            super.scroll(to: newOrigin)
        } else {
            setBoundsOrigin(newOrigin)
        }
    }
}

class OutlineView: NSOutlineView {
    private var arrowKeysDown = Set<UInt16>()
    
    override func keyDown(with event: NSEvent) {
        if (125...126).contains(event.keyCode) {
            arrowKeysDown.insert(event.keyCode)
            (enclosingScrollView?.contentView as? ClipView)?.isScrollAnimationEnabled = false
        }
        super.keyDown(with: event)
    }
    
    override func keyUp(with event: NSEvent) {
        super.keyUp(with: event)
        arrowKeysDown.remove(event.keyCode)
        (enclosingScrollView?.contentView as? ClipView)?.isScrollAnimationEnabled = arrowKeysDown.isEmpty
    }
}

Yeah, you're probably right, feel free to modify it in any way :)