Hello again Richard! I have some good news for you.
The latest version of the in-game panel supports exactly this feature. When a flightplan and the panel is opened, it will ask you if you want to load the flightplan into charts. You can also load it the usual way, in the “Add flight” menu using a button labeled “From simulator”.
Thank you for the suggestion! If you’re interested in what else changed with the latest update, have a look in this thread: