Game concept · Accolades
Knight Army Modifier
The game also links it as Knight Army Modifiers.
From the game's encyclopedia
An effect applied to any Army which contains the pertinent Acclaimed Knight.
The Knight need not be their Army's Commander for their Knight Army Modifier to apply.
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.
Knight Army Modifier is an entry of Crusader Kings III's in-game encyclopedia (Accolades). The game explains it: "An effect applied to any Army which contains the pertinent Acclaimed Knight." It is part of Accolade. The game also links it as Knight Army Modifiers. Patch 1.20.1.2, from game/common/game_concepts/04_ep2_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/04_ep2_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.