Game concept · By God Alone
Stability Chapter
The game also links it as Stability.
From the game's encyclopedia
A Stability Chapter is rare daylight for The Christian Church:
Building in a Temple Holding is cheaper, Grand Cathedrals progress faster, Characters are more likely to become a Monk, and the Great Schism may get mended.
Concord is the only Stability Chapter.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Stability Chapter is an entry of Crusader Kings III's in-game encyclopedia (By God Alone). The game explains it: "A Stability Chapter is rare daylight for The Christian Church:" It is part of Chapter Type. The game also links it as Stability. Patch 1.20.1.2, from game/common/game_concepts/pam_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/pam_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.