I know that in the game you can split a stack into singles by holding Shift and dragging the whole stack to an empty space, then select one, then select ok. But this is a long arduous task, if you're wanting to send out a single free item to all of your kin-mates as a mailer. I think this is a great opportunity to simplify the inventory management by making a single button in the Shift-drag menu which would say something along the lines of Split stack into singles, or ones.... The split stack would occupy any free space in the inventory bags, and then you can mail stuff out much much quicker.
If anyone is willing to look into this, or has an opinion on this, please leave a comment down below!