The TakeDictionaryValueTransformation allows us to get the value of a key-value pair by providing the key e.g. get value from extracted metadata where Metadata is a dictionary and you provide the key xmpMetadata to get the whole xmp metadata values back, followed by another TakeDictionaryValueTransformation to get the Dublin Core values when providing the key dc. 

You have to repeat the TakeDictionaryValueTransformation multiple times in come cases, until you get the value and no longer an object. 

Check the JSON structure in the Display Pattern Editor to see the key-value pairs: 

• key: xmpMetadata; value: [object]
• key: dc; value: [object]
• key: rights; value: [object]
• key: x-default; value: "creator of the file"

Specific Definitions

From XMP get Dublin Core (dc), then get Creator from Dublin Core

"transformations": [
    {
        "kind": "TakeDictionaryValueTransformation",
        "key": "xmpMetadata",
        "traceRefId": null
    },
    {
        "kind": "TakeDictionaryValueTransformation",
        "key": "dc",
        "traceRefId": null
    },
    {
        "kind": "TakeDictionaryValueTransformation",
        "key": "creator",
        "traceRefId": null
    }
],
    "storeIn": "dcCreators",
    "traceRefId": null