Hello @JakeObrien  Yes, You will have to use the API to update these attributes. The Payload would look like this:
"data": {
    "type": "profile",
    "id": "01GDDKASAP8TKDDA2GRZDSVP4H",
    "attributes": {
      "email": "sarah.mason@klaviyo-demo.com",
      "phone_number": "+15005550006",
      "first_name": "Sarah",
      "last_name": "Mason",
      "organization": "Example Corporation",
      "title": "Regional Manager",
      "image": "https://images.pexels.com/photos/3760854/pexels-photo-3760854.jpeg",
      "location": {
        "address1": "89 E 42nd St",
        "address2": "1st floor",
        "city": "New York",
        "country": "United States",
        "region": "NY",
        "zip": "10017",
        "timezone": "America/New_York",
        "ip": "127.0.0.1"
      },
      "properties": {
        "newKey": "New Value"
      }
    },
    "meta": {
      "patch_properties": {
        "append": {
          "newKey": "New Value"
        },
        "unappend": {
          "newKey": "New Value"
        },
        "unset": "skus"
      }
    }
  }