With the "GSX Handling" option enabled on the RJ's EFB, the door opening/closing is something that is controlled entirely by GSX. The GSX software makes a request for those doors to be opened/closed, and then they are opened via our code.
You could try removing the L2 door from each of the RJ's GSX Profiles (located at ...\Community\justflight-aircraft-rj\Documents\GSX Profiles) and see if that provides what you are looking for. You would just need to replace the text under the [exit4] field with "remove = 1".
We would recommend making a backup of the original GSX profiles first just so you can revert to them if anything doesn't work out. You can also reinstall the RJ to revert to the original GSX Profiles.
Mark - Just Flight