NSPopover to start in a detached state

Is there a way to force the NSPopover to start in the detached state? I only see isDetached which is a read-only property for the state of the popover and an NSPopoverDelegate method detachableWindow(forPopover:) which lets me override the window that gets created. I'd like to essentially click a button and have the NSPopover start in the state in this photo.

The style of this window is exactly what a product requirement is and I can't seem to find any NSWindow style settings that would make a window do something like this (nor an NSPanel)

This detached popover functionality seems special in that it:

1. non-modal, but stays above main app. Able to still interact with the main app just like in Messages how you can still click around and type a new message.
2. Clicking another app, AppFoo, puts both the main app and the helper window behind AppFoo.
3. The helper window can be moved around and isn't hidden on app deactivation (another app gets selected).
4. Has the little, native, grey X in the top left.

Here is the trick. Use the required delegate method detachableWindowForPopover: to do the work for you, like:

- (void) showPopoverDetached
{
    NSWindow* detachedWindow = [self detachableWindowForPopover:nil];

    [detachedWindow.windowController showWindow:nil];
}

Seems that the Apple engineers implemented detachableWindowForPopover: on a pretty smart way, I guess it uses the content view controller class, and will always create a singleton like instance of the detached window. Once detachableWindowForPopover: has called the presented window instance will be re-used no matter when and why it is called, called it directly (from a func like my sample above) or indirectly (e.g. when you drag out, detach, the popover from its original position)

This way they can prevent a popover from being detached 'twice' and we can also implement the detached way programmatically, nice job from them!

Here is a tiny demo of how it works in a real life (tested on macOS 10.13 - 13.0)

https://i.sstatic.net/hej75.jpg