My understanding is that you can only “link” one account. if you wish to link another, you most “unlink” the first to link the second. Additionally, you only gain the recipes that were claimed by the account that is currently linked. So if you have recipes claimed on multiple Twitch accounts, you will never have access to all your claimed recipes at the same time. For this reason, it would be wise to only claim rewards on one Twitch account. Linking can only be done from the game menu within Conan Exiles (not from Twitch). Hope this helps.
PS ~ Welcome to the forums!