Ghost42, I have no idea where the edit folder is but dragging the tzarc icon over in Content Manger to the route where the session would be should work but hasn't. Yes, I did a dbr and an extended dbr with no luck.
Your editing folder is found wherever your content is located.
On the Launcher, click on Trainz settings.
Click on install.
You'll see the path where your data is found.
Click on the path and then press CTRL+A to select it.
Press CTRL+C to Copy the information.
Open up Windows Explorer.
In the bar at the top where it shows This PC >
Click on that and paste in the path by pressing CTRL+V
Open up the editing folder.
Put the .tzarc file in the editing folder.
At the Launcher, run a Database repair.
This will add your session back in.
If getting to your user data folder is still a no-go, there are other ways to do so.
Check in Content Manager to ensure that the session is there and submit if it's open for editing.