WindowsのIME関連の技術情報がまとまってるすごいサイト見つけた＞＜
IMEハッカーズ☆
https://katahiromz.web.fc2.com/colony3rd/imehackerz/ja/

katahiromz/imehackerz: IME Hackerz by katahiromz
https://github.com/katahiromz/imehackerz