How To Get Rid Of Items For Quests Already Completed?

So, I did /fixquests in an attempt to get a quest item I thought I was missing, didn't get said item, and now I'm stuck with 16 quest items for quests I completed ages ago. How do I get rid of them?

 

Either fill your inventory up with emeralds until you're holding the quest item with a full inventory, then drop it and it should disappear, or throw them into your daily chest and close it.

 

Or this:

Place the item(s) in the 2x2 crafting area of the inventory. Fill the rest of the inventory with items (most likely emeralds). Close the inventory and
the quest items will be gone.

 

I shall try this, thanks.