Defining a window that never activates

Hello. I’m trying to make a floating window to never activate. It has no control anyway and I’d like it to not steal the focus.

I tried both of these, but they are read-only:

(I’m not sure which one would be correct, as “key” and “main” look synonymous to me).

So they’re read-only and I can’t find how to change them otherwise, except using the NSWindow’s constructor, but I already have the window existing.

I also found self.NSPanelMBS.becomesKeyOnlyIfNeeded=true, but it doesn’t look to change anything (and the documentation seems poor for this).

What’s the key to change these properties?

I am too looking into this. Actually, I’ve been looking for a solution for some time as I posted the same question some months ago. Basically, I need to have a floating window behave as a non-activating panel, just like a popOver panel.

I suspect something has changed since Big Sur because I remember it worked on earlier systems. From the answers I found on StackOverflow, it would seem that you should subclass NSPanel and override the CanBecomeKeyWindow to return False.
The problems is, I am not sure how to do that in Xojo…