Sheikah Converter is a project that comprises a library and a CLI tool to convert
The Legend of Zelda: Breath of the Wild save files between console formats (Wii U <-> Switch)
To learn how to install and use the packages from Sheikah Converter, check the documentation on the links above.
The library part of Sheikah Converter is based on DeltaJordan's BotW-Save-Manager.
Also, the save files used on the tests were taken from Torphedo's BOTW-CompletedSaveFile. Those were extremely useful for debugging, as Torphedo provided save files for both consoles.