Well, that the squares go blank again when you press one of the buttons is intended behavior. But the Betza notation for the cleared squares should appear in the text entry 'Betza move description' just below the table from which you select pieces. E.g. if I click the square above the star piece and press the move-only button, the text fmW should appear there. If I then click the squares diagonally above the star piece, and press capture-only, the text should change to fmWfcF. I have no Mac where I can test this, but on my PC it works with FireFox, and on my Android tablet with the Android browser it works too.
Well, that the squares go blank again when you press one of the buttons is intended behavior. But the Betza notation for the cleared squares should appear in the text entry 'Betza move description' just below the table from which you select pieces. E.g. if I click the square above the star piece and press the move-only button, the text fmW should appear there. If I then click the squares diagonally above the star piece, and press capture-only, the text should change to fmWfcF. I have no Mac where I can test this, but on my PC it works with FireFox, and on my Android tablet with the Android browser it works too.