I think this topic will help you understand how Shotcut works a bit.
I also think that for your needs you need another program maybe GPU assisted for video editing, converting.
You can check out Davinci Resolve, free or paid versions.
But you probably don’t need a typical video editor. A video converter should suffice (sometimes with simple, very limited video editing). Unfortunately, Avidemux doesn’t seem to support AV1.
Handbrake converter (wikipedia) may be the solution for you.