Sadly it's not something you can do at the moment. However if you just want to take a quest item from a chest and you don't actually need the item for anything other than the quest(you're not using it as a sword or armor or whatever), you can reskin an NPC to look like a chest.
Then set the npc (chest) to disapear. Then in the dialogue write that you take the item and set the variable to whatever you want.
That's how I make my quest items.