is_a_previous_title_holder_trigger

is_a_previous_title_holder_trigger = {
	save_temporary_scope_as = previous_holder_compare
	$TITLE$ ?= {
		# Easy out
		trigger_if = {
			limit = { previous_holder ?= scope:previous_holder_compare }
			always = yes
		}
		# Hard out
		trigger_else = {
			any_past_holder = { this = scope:previous_holder_compare }
		}
	}
}

As written in game/common/scripted_triggers/10_tgp_japan_triggers.txt.