Hello we have some information on our Getting Started support page which shows the various difficult levels for locos, tutorials and scenarios, I've linked it below - is this what you are referring to? Getting Started Support Page https://dovetailgames.freshdesk.com...rted-with-train-sim-world-4#Learning-the-Game
That's the scenario difficulty rating which has always been there. He means the new loco difficulty. I think I saw it in the training centre menu somewhere but loco difficulties are subjective so I am always going to ignore them anyway. Probably the least useful new feature.
I just had a quick look and when you go to the training page where the locos are listed they all have a difficulty rating on the right hand side. They are all either 1 or 5 though and I would disagree with most. The 185.2 has a rating of 1 while the 185.5 with MRCE livery has a rating of 5! Edit: They are on ALL loco selection pages not just in the training menu.