just treat it all the same way you save items but with a different struct.
So S_Item is (class,transform)
S_Chest is (class,transform, inventory)
S_NPC is (class, transform, NPCDATA)
etc
on save you get all actors of X (X is item, npc, chest) calls its save function (item, chest, npc) etc
on load you spawn class at transform and set optional data (inventroy/NPCDATA) etc