Game concept
Promote Cultural Acceptance
The game also links it as Promoting Acceptance.
From the game's encyclopedia
Promote Cultural Acceptance is a Councillor Task performed by the Steward.
It increases the Cultural Acceptance between the target Culture and the Ruler's Culture.
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.
Promote Cultural Acceptance is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "Promote Cultural Acceptance is a Councillor Task performed by the Steward." It is part of Councillor Task. The game also links it as Promoting Acceptance. Patch 1.20.1.2, from game/common/game_concepts/00_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/00_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.