@Troy Tessalone , maybe I am pressing my luck, but if you are able to help me with this one as well, I would super appreciate it!
This situation is more complex.
Concept is to append data to existing selections for the multiselect field.
You’d have to first Find the Person to get the existing field values, then append the new selection, which you can try to do using a Custom value and comma separating the input values.
As an alternative, you could split each option within the 1 field to instead be it’s own field, which might be a better way to handle your use case.
Otherwise, likely will need to involve the Pipedrive API: https://developers.pipedrive.com/docs/api/v1/