What is the best way to store and manage tahini?
The oil will always separate from the rest of the product. (home made or natural/bio peanut butter will behave the same way)

When that happens, just spend some time and elbow grease to mix it back together again.

if the tahini was stored in the fridge, it might take longer because everything will be harder.

Just leave it on the counter for a while until it gets to room temperature before mixing it back together.

(after googling) People suggest to keep the jar upside down and when you want to use it, just put it back straight and let it stand for a while, it will mix itself (a little bit) together again.