There is a workaround I've done to create the exact same thing you want.
You can check my game if you'd like to see how it behaves.
So, here's what I did:
- Add a DrawingCanvas plugin into your project, place it in your scene, adjust the size/position, and disable its visibility.
- At the desired moment in your code, use the Paste object action from DrawingCanvas and add all the objects you want to be shown in your downloaded image. Then use the Save image action which is going to save your current canvas image.
- Finally, after waiting for that action to finish (whether using Wait action or On saved image trigger) you can call the Invoke download action from the Browser object passing DrawingCanvas.SavedImageURL expression in the URL field.
Well, that's pretty much it. I hope I was clear enough :)