Here's the DTG page that has them all on: https://live.dovetailgames.com/live/train-sim-world/articles/article/tsw-help
I'm pretty sure that page includes all the manuals that have been made. Some routes do not have manuals, mostly the most recent ones, but this is on the roadmap so they might have some created for them in future.
There are some guides made by members of the community, if those are what you're thinking of. To find these, search the word guide in the forum search bar for thread titles only and most of the threads that include them should come up.
DTG Protagonist Can the LGV manual be added to the manuals page on Dovetail Live? Lots of people have been looking for it. It’s one thing not having a manual but another having one that’s available but still not listed. While I’m on the subject, could that page name (the link in the menu) be changed from ‘Guides’ to ‘Manuals’ or ‘Manuals and Guides’ as I think most people call manuals manuals not guides, so that’s the word they will be looking for in a link. Ta.