If Steam Guard is used, you need the STEAM_AUTH_CODE secret. Follow this url as a guide:
https://github.com/SteamTimeIdler/stidler/wiki/Getting-your-%27shared_secret%27-code-for-use-with-Auto-Restarter-on-Mobile-Authentication#getting-shared-secret-from-ios-windows
You need to either switch to Steam Desktop Authenticator or extract the Shared Key secret from your phone's files.
If Steam Guard is not used, STEAM_LOGIN and STEAM_PASSWORD will be enough.
Uploads are done via the official NexusMods v3 API and only require an API key. Get one at https://www.nexusmods.com/settings/api-keys - this is our NEXUSMODS_APIKEY (NEXUSMODS_API_KEY for the verify workflow) secret.
Session cookies (NEXUSMODS_SESSION_COOKIE) are no longer used - the cookie-based refresh-unex-nexusmods.yml and verify-nexusmods.yml workflows were removed.