Is there any way to set ownership to every item in a cell without having to individually click on each item to set it? I imagine that Tes4edit would be the tool I need, but could anyone tell me how?

On the toolbar >World >cells
Find your cell in the list.

On the Interior Data tab, you set either the Owner NPC or Owner Faction.

All items in the cell aquire ownership from the cell if its not set on the item.

Thanks