Note that Sjaak exceeds WinBoard's capacity for displaying engine-defined variants in a rather spectacular way. So not all such variants are displayed, but those that are not can still be selected with the -variant option.Ferdy wrote:
Variants defined in Sjaak's variants.txt are printed before the built-in variants, so they have a better chance to show up in WinBoard's New Variant dialog, but even then some variants at the bottom of that file cannot be displayed.