Flexible castling is nothing else but multiple castling moves with different ranges on the King. E.g. KisO2isO3isO4. It is not a special way of castling, such as fast castling or free castling would be. So it has always been supported, ever since a notation for castling was added to Betza notation.
Flexible castling is nothing else but multiple castling moves with different ranges on the King. E.g. KisO2isO3isO4. It is not a special way of castling, such as fast castling or free castling would be. So it has always been supported, ever since a notation for castling was added to Betza notation.