SUMMARY In particular, I wanted to use QJSValue type, so that I can call QML methods from the Rust side.
Calling QML code from Rust is out of scope. The design of RQBG is such that you can crate a data model in Rust, but the Rust does not know about the QML code. You can trigger functions in the QML by binding to property states. Calling QML from Rust is out of scope for the current design. However, if you have ideas for doing this is in a safe and simple way, I might add it.