Hello,
Yes, we will add the request key feature later on the new version on itch that will match the version number from steam. If that feature doesn't work then we will send out an e-mail or ask for people that bought the game and want the version on steam to send us an e-mail.
Either way, the build/version on itch is the same one that will be on steam.
Hope that helps.
Best Regards,
Cursed Atelier