is there a way to have a platform-native context menu (right-click menu)?

These two are separate concepts. Do you want a Compose pop-up that can go outside the window bounds or do you want to invoke a platform native pop-up?

I want the platform native pop-up

Then you'd need to find those platform-specific APIs for each platform and provide JNI bindings for them.

and how do you do the former?

What's the former? A Compose popup that goes outside the main window bounds?

Yes

You would use a

ComposeWindow

, configuring its size and position based on your content, your anchor location and the screen size.