A while back, compatibility was added for the In-Game Wiki mod: https://www.curseforge.com/minecraft/mc-mods/in-game-wiki-mod

The mod may still work for 1.12.2 and 1.10.2 but as of December 2020 it has not been updated in over two years (four years for the 1.10.2 version). In its current state, IGW is not usable for newer Forge versions or Fabric versions. In addition, the IGW developer appears to no longer be active on Curseforge, so updates and/or bug fixes are unlikely to happen at this point.

As newer and more complex features are implemented into Immersive Railroading it will become more important to provide in-game documentation explaining how everything works.

There are a couple solutions to this problem:

1. Use a different documentation mod. Patchouli seems like a good candidate since it is still actively maintained, available on newer MC versions, and has a Fabric port:

https://www.curseforge.com/minecraft/mc-mods/patchouli
https://www.curseforge.com/minecraft/mc-mods/patchouli-fabric

However, Patchouli is not available for Forge 1.7.10, 1.10.2, or 1.11.2. It is also unavailable for Fabric 1.14.4.

Guide API is another option, with releases available for all (Forge) versions that IR supports:

https://www.curseforge.com/minecraft/mc-mods/guide-api
https://www.curseforge.com/minecraft/mc-mods/guide-api-village-and-pillage

As of December 2020 it has no Fabric port, and releases for older MC versions are no longer maintained.

2. Develop an "in-house" alternative, either as a separate UMC-based mod or as a feature integrated directly into IR or UMC. This would require more work but would ensure compatibility with all present and future IR versions.