Game concept
Activity Option
The game also links it as Activity Options.
From the game's encyclopedia
All Activities have Options that allow you to customize the planning of your activity. Options have various costs and requirements.
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.
Activity Option is an entry of Crusader Kings III's in-game encyclopedia. The game explains it: "All Activities have Options that allow you to customize the planning of your activity." It is part of Activity. It covers Long Hike. The game also links it as Activity Options. 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.