Deleting Sessions Also Deletes Other Sessions

When I delete some of the sessions I had saved, it also deletes sessions saved later. This is not always the case. How do I know when deleting a session will delete others?

I am attempting to run an "endless" session, always continuing from where I had left off previously. I had done this using Trainz 2012, running a session for literally years. Typically, I kept ten previous saves, and deleted any before that. I don't know how to run an endless session in Trainz 2019. How can I do this without taking the chance of deleting sessions I don't want deleted?

Thank you for your help.
When I delete some of the sessions I had saved, it also deletes sessions saved later.

Those "extra" sessions that are being deleted are most likely (almost certainly) saved Driver Games. When you are in Driver mode and save the Session you are running, the current position of all trains, the state of all wagons (loaded/empty), industries (products and product levels) and the status of all the Session Rules (completed/not completed) is saved in a Driver Game that is linked to the Session you are running.

If you delete the Session you will also delete all its saved Driver Games. Just as if you delete a Route you will also delete all its Sessions (if any) and all their saved Driver Games (if any).

How do you tell if a "Session" is actually a "Driver Game"? Normally, a Driver Game is saved with a name that includes the Session name, the time and date it was saved and the play duration. For example

"TGR Fingal Session 4: Conara Mixed Goods - 21:57, 27/2/2024 - 41:17"

But when you save the Driver Game you can overwrite that and enter your own name which may not include any date/time details. This would make identifying it as a Driver Game and not a Session more difficult.