i have tsw 2 with the tees valley line dlc, i would want to make a custom livery for the class 101 train but it doesn't show up in the selection menu.
He means until Dovetail say you can paint any of the preserved collection rolling stock you are stuck with what's in game.
It's not a bug the preserved collection can't be used in the livery editor. I'll summarize it for you, TSW 2020 content/DLC= Preserved collection. Preserved collection can't be used in the livery editor simple
The "Preserved Collection" are the old TSW 2020 DLC moved to TSW 2. You can't use these TSW 2020 DLC in the Editor yet, even they are in TSW 2 now. Check the Roadmap section "in production" for more infomation.