Append values to multi-select field via Update Ticket API

Hi,

I have a multi-select dropdown with multiple values (ex. value1, value2, value3).

I would like to update this field via the update ticket API call, that will add one of the values. For example, one call from one source will append value1, the second call will append value2, etc.

The issue I am seeing is that whenever the Update Ticket API is run it just replaces the existing value in the multi-select dropdown, as opposed to appending the value.

Looking at the documentation on this topic, I don't believe this is possible. Can anyone confirm if there is an option to append a value to a multiselect dropdown via the API?