Updating a connected field through Zapier

Hello guys, hope you are all well.

I’m having a hardtime trying to update a many-to-many connected field using Zapier.

I have two objects: Providers and Patients. The provider object has a patient field connected to the patient object. I want to append a new Patient to a certain Provider, but keeping the previous connected patients of this provider untouched.

When I use my usual methods in zapier, the provider > patient field goes blank.

I’ve tried a intermediary step “search a record” just to keep the previous data and append the new patient, no dice.

Does anyone have an idea for a solution? Thanks a lot for you attention