Loot menu where you drag items in and you could add % for each item and to define how many items can drop on death from the list

Thanks for the request. At the moment the NPCs has no loot table support.
Loot tables would be supported by looting mods a loot menu however would be a "custom" looting and will not be supporting any looting mods at all.

Would supporting loot tables working as well or does this needs to be a extra menu ?