So glad you put this manual together I just found this after struggling to figure out what I was doing wrong.
Add Road, Rail and River:
Pending
Roads, Rivers and Railroads are set under the "Paths" Tab.
Currently, rivers are the most complete path, but none of the paths show in-game at this time
I was trying to make a nice looking river since the terrain is at around 200ft in this area and added a nice river path that looked ok. I was going to start adding bridges and went into offline practice to take a look and nothing .
Then jumped into the manual and it says it won't show. So I guess I can't use that at all.
To add more detail, I was trying to make a river skinny enough so that the bridge objects could go over them, but trying to make it with the smallest brush size in terrain that's 200feet up, I can lower the terrain near the water but I can't make it look good, and not have right angles or smooth out in some area..it's very jaggy or straight line.
I used create all beaches to try to smooth it out but for some reason it never fixes the north side of the river, only the south comes out really nice.
So scratching that idea till later and will just add more buildings... The idea was adding objects that ww1 planes could fly around and under even..Just for fun.