OTM - Any option to store mixed case data?

Summary:

We have a tracking vendor sending a URL via a Tracking Event that we'd like to store with/on the shipment. That URL contains a mixed case generated key/uuid query parameter that is specific to the shipment. Tracking Event Refnums are automatically converted to uppercase so the key/uuid is changed and doesn't load the intended shipment. Is there any other element/field that could be used that would maintain a mixed case value? Any property settings to allow mixed case data?

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