User defined variants in WinBoard

Setup

If you have not done already, follow the steps in https://github.com/fairy-stockfish/Fairy-Stockfish/wiki/Graphical-user-interfaces#xboardwinboard to set up an up-to-date (>=4.9) Winboard or XBoard together with Fairy-Stockfish.

Adding variants

1. Download the variants.ini from the latest release.
2. Open variants.ini with a text editor and add the variants you wish from https://github.com/fairy-stockfish/Fairy-Stockfish/wiki/Variant-configuration by copying and pasting the code into the variants.ini, or add your own variant configuration in the file.
3. Now go back to Winboard.
4. Go to Engines>Edit Engine List... and copy&paste your entry for Fairy-Stockfish into a new line, e.g., "Fairy-SF" -fcp "C:\fairy-stockfish-largeboard_x86-64.exe". As a preparation for the next step, you should set the working directory (-fd) for the engine separately instead of including it in the path of the engine, e.g., "Fairy-SF" -fcp "fairy-stockfish-largeboard_x86-64.exe" -fd "C:\".
5. In order to load the variants.ini file, you need to add load variants.ini to the command. E.g., "Fairy-SF-custom" /variant=indiangreat -fcp "fairy-stockfish-largeboard_x86-64.exe load variants.ini" -fd "C:\". This assumes that the variants.ini is in the same directory as the engine.
6. Modify the /variant=... part from step 5 to the name of the variant you want to play.
7. Click on Engines>Load New 1st Engine... and double click on the name of the line you just added, e.g., Fairy-SF-custom.
8. If your variant has unorthodox rules for which Winboard does not allow you to put in the moves, go to Options>General... and uncheck Test Legality. If you do this, be careful to not make illegal moves on the board, otherwise you might need to reload Fairy-Stockfish or restart Winboard to recover it.