There are 2 repositories under modding-library topic.
Next generation modding platform for Final Fantasy VII and Final Fantasy VIII ( with native Steam 2013 release support! )
Modding API for games made by Illusion (PHAPI / KKAPI / ECAPI / AIAPI / HS2API / KKSAPI)
Config based patch management for Subnautica and Subnautica: Below Zero
A work-in-progress modding tool geared toward UNDERTALE/DELTARUNE
MT Framework and RE Engine format library and toolset.
Adds modding components to RimWorld: vehicles, spell casting, weapon slots, oversized weapons, and more!
Apex Engine Format Library
Config based patch management for Graveyard Keeper
Next generation modding platform for Chrono Trigger ( native Steam 2018 release support! )