fp2_struggle_compromise_transfer_duchies_effect

fp2_struggle_compromise_transfer_duchies_effect = {
	title:e_spain = {
		while = {
			limit = {
				any_in_de_jure_hierarchy = { fp2_struggle_compromise_transfer_duchy_trigger = yes }
			}
			every_in_de_jure_hierarchy = {
				limit = { fp2_struggle_compromise_transfer_duchy_trigger = yes }
				add_to_list = transferred_duchies
				# To ensure kingdom's capitals are always inside them
				if = {
					limit = { title_capital_county = kingdom.title_capital_county }
					kingdom = {
						save_scope_as = old_kingdom
						if = {
							limit = {
								any_direct_de_jure_vassal_title = {
									NOT = { is_in_list = transferred_duchies }
									title_capital_county.kingdom = scope:old_kingdom
								}
							}
							random_direct_de_jure_vassal_title = {
								limit = {
									NOT = { is_in_list = transferred_duchies }
									title_capital_county.kingdom = scope:old_kingdom
								}
								title_capital_county = { save_scope_as = new_capital }
							}
							set_capital_county = scope:new_capital
						}
					}
				}
				if = {
					limit = { title_capital_county.holder.top_liege.primary_title.tier = tier_kingdom }
					set_de_jure_liege_title = title_capital_county.holder.top_liege.primary_title
				}
				else = { set_de_jure_liege_title = title_capital_county.holder.top_liege.capital_county.kingdom }
			}
		}
	}
}

As written in game/common/scripted_effects/03_dlc_fp2_scripted_effects.txt.