Thanks for posting. It's not possible to import files into Strava using the Strava Mobile App. To import files, it's necessary to sign into your account on the Web and navigate to this link:
I hope I've answered your question, let me know if you need more information.
Why is this functionality still not available via the mobile app?
Its like Garmin, only some stuff available in web and some in app. What is it with these fitness companies?
So you end up needing both. Does not help that Strava website is not mobile friendly.
Maybe advances in AI will help Strava out with the missing code?