You can use voice commands to create a shopping list, but it's not in Keep. I've never had luck at adding stuff to stuff in Keep with voice commands. But the shopping list never fails. It's part of the Google Home app and is stored there, you can add and view it w/your voice (OK Google add cereal to my shopping list or OK Google show my shopping list). You can also access it in the Home app for manual updating etc.
edit: only the primary list will be updated by voice, no matter how many you have named.