How to get display value of multi select custom field

Hi Andrea. You can accomplish this by utilizing a stream transform. In particular you want replaceOptionValuesWithDisplayNames.

stream: {
    $id: "location-stream",
    filter: {
      savedFilterIds: ["xxx"],
    },
    fields: [ "id", "name", "slug", "c_options" ],
    "transform": {
        "replaceOptionValuesWithDisplayNames": [
            "c_options"
        ]
    },
[...]