If you create the reminder within a smart list, it will automatically add the tag of that list to the item.
Example: I have three priority lists. If I tap/select the low priority list and make a new reminder, it will auto populate the tag for low priority.
This works with Siri as well.
“Hey Siri, add ______ to my high priority list” Siri will then add the reminder with the high priority tag associated with that list.
I hope that helps!