But surely you must have noticed this new arrangement in every new alert and dialog in every application in Big Sur? This isn’t a Panorama change, it’s system wide. Panorama is just “going with the flow” and supporting the Apple user interface conventions.
I think the reason the first one has side by side buttons is because you specified a width of 300 for the text editor. But the layout arrangement is all controlled by Apple. I’m not sure what you would actually search for, but I’ve seen dozens of examples over the past year of people complaining about how these alerts are layed out. Clearly someone high up at Apple things this is great It does make it more difficult to tell apart an iOS app running on Big Sur from a native macOS app.
Actually, this statement has always been limited to 3 buttons (because the underlying Apple API only supports 3 buttons). So the Cancel button hasn’t run off the bottom, it simply is ignored.
The fact that only 3 buttons are supported is mentioned in the documentation. However, perhaps it should cause an error if you specify more than 3 buttons? I’m not sure if that would be an improvement or not.
If you want to control the layout yourself, rather than leaving it up to Apple, the only choice is to create a form and use rundialog.
Another option would be to use the supergettext statement, which does use a form so the layout hasn’t changed (the buttons are still arranged horizontally). However, this statement is also limited to 3 buttons – so I think for this application you probably will need to create a custom form for this dialog.