Hi @Martina_Kudelcikova,
Thanks for posting, and welcome! I believe you’re referring to this article that covers all of the steps to use Zapier to create a daily summary of changes to your base. These instructions are still up-to-date, but there was an interface change that is slightly different than shown in the article. The custom value should still be an option, but it’s now found in a tab up top when selecting the record:
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I hope this fixes the issue for you!