gather_contributors_in_list_effect

gather_contributors_in_list_effect = {
	every_contribution = {
		limit = { contribution_is_funded = yes }
		contributor = {
			if = {
				limit = {
					scope:great_project = {
						trigger_if = {
							limit = { has_variable = plundered_contributors }
							NOT = { 
								is_target_in_variable_list = {
									name = plundered_contributors 
									target = prev
								}
							}
						}
					}
				}
				add_to_list = contributors_to_reward
			}
		}
	}
}

As written in game/common/scripted_effects/tgp_mandala_scripted_effects.txt.