Which feature you means? Scan barcode to enable filters on power bi mobile app reports or direct recognize barcode?
AFAIK, current power bi mobile for uwp version not contains scanner features. Hololens also use uwp version, I'm not so sure if power bi mobile team release a specified for hololens.
Power BI App for Mixed Reality does not support barcode scanning. It does support QR code scanning, but at this point without URL query string filter.
if you find this a feature that is missing in the app, please add your vote to our user voice website: https://ideas.powerbi.com/forums/265200-power-bi-ideas?category_id=105939