pub struct NativeOptions {
    // ... other fields ...
    pub persistence_path: Option<PathBuf>,
    /// Override the default storage creation with your own custom storage implementation
    pub storage_creator: Option<Box<dyn Fn() -> Option<Box<dyn crate::epi::Storage>>>>,
}

fn init_run_state(
    &mut self,
    event_loop: &ActiveEventLoop,
) -> Result<&mut GlowWinitRunning<'app>> {
    profiling::function_scope!();

    let storage = if let Some(storage_creator) = &self.native_options.storage_creator {
        storage_creator()
    } else if let Some(file) = &self.native_options.persistence_path {
        epi_integration::create_storage_with_file(file)
    } else {
        epi_integration::create_storage(
            self.native_options
                .viewport
                .app_id
                .as_ref()
                .unwrap_or(&self.app_name),
        )
    };

    // ... rest of function
}