Does anybody know what the OK button is meant to do on the Chord Options dialog?
(I'm using build 1111)

Appears to do nothing. Same as the "Apply" button in the Bars Settings Menu (F5). I do believe this has been discussed here in the recent past. But I tend to have stopped even noticing these foibles in BIAB. We talk and talk, but these type of items don't change.

Yes, I reported that this didn't seem to have an effect, and the action in the dialog box happens anyway. As I recall, there are a few others like this. For example, in Bar Settings, the entry for 3 beats per measure will 'apply' without clicking on Apply (and there is no OK button anyway in this dialog box).

There's also two 'apply' buttons in the Bar Settings dialog. I think that has been reported.

It's long puzzled me that Windows rarely, if ever, has the "Dismiss" button that's common on Unixen for closing the dialog with no further consequences. Both OK and Cancel have potential ambiguities.

Apply - Apply the changes and keep the dialog open.
OK - apply the changes and close the dialog.
Cancel - Abort the changes and close the dialog.
Dismiss -- Just close the dialog.

Yes, we took exactly that approach when programming applications for DEC VAXes and Alpha's in OpenVMS. It's not a new approach. It's simply very intuitive.
Maybe we have become a little conditioned. OK just means 'get on with it'. Not the right amount of choices can be subjective.

Indeed; far from it ... I think it predates graphical user interfaces.

Just for educational purposes, could someone give an example why Dismiss would be needed when Cancel wouldn’t do the same thing?