There is a lot of good information in the link pware provided. To me, the following is the most important...
Route Layers vs Session Layers
This topic has filled endless threads in the Trainz Forums with arguments raging on both sides.
There are no "cast iron" rules that dictate what should be placed in the Route Layers Group and what should be placed in the Session Layers Group. Each Route and Session will be different and different creators have different ways of working. The main question to be asked is how many different Sessions will be created using a particular Route?
Many creators only ever build a single Session for each of their Routes so they do not use Session Layers at all.
- For a Route with multiple (2 or more) Sessions - certain things will probably need to go into the Session Layers Group for each Session.
However, the most critical piece of information is missing. This is regarding the default "Active Layer". Anytime you add "stuff" in Surveyor, it goes into the Active Layer.
A. If you Select Route / Edit Route, the default Active Layer is the Route Layer.
B. If you Select Route / Select Session / Edit Session, the default Active Layer is the Session Layer.
What that means is:
If you get into Surveyor using option A, and don't change anything in the Layer options, everything you add to your layout will go into the Route Layer.
If you get into Surveyor using option B, and don't change anything in the Layer options, everything you add to your layout will go into the Session Layer.
I always have only one Route/Session. For Route named BigGap I'll have one Session named BigGap Sess
I put everything into a Route Layer.
To get into Surveyor, I Select Route BigGap/ Select Session BigGap Sess/ Edit Session. I then
immediately* go into the Layers Tab and select the Route Layer as the Active Layer.
I add stuff to my layout; click QuickDrive; save Route and Session; see how things are working; exit back into Surveyor mode (it still has the Route Layer as the Active Layer).
*If I forget, as I often do, as soon as I remember, I go into the Layers Tab and merge the Session Layer into the Route Layer.
I do make use of multiple Route Layers as described in the wiki. But that's for another thread.