tournament_choose_jockey_effect

tournament_choose_jockey_effect = {
	save_scope_as = chosen_jockey
	if = {
		limit = {
			NOT = { is_participant_in_activity = scope:activity }
		}
		hidden_effect = { add_to_activity = scope:activity }
		scope:activity = {
			add_to_guest_subset = { name = spectator target = scope:chosen_jockey }
		}
	}
	every_in_list = {
		list = potential_jockeys
		limit = {
			NOR = { 
				this = scope:chosen_jockey 
				this = root
				has_character_flag = generated_jockey
			}
		}
		add_opinion = {
			target = root
			modifier = disappointed_opinion
			opinion = -10
		}
	}
	root = {
		set_variable = {
			name = horse_race_jockey
			value = scope:chosen_jockey
		}
	}
}

As written in game/common/scripted_effects/04_dlc_ep2_tournament_effects.txt.