I use these bobbins too, and while they do come undone a little, I don’t really worry that much. I just tuck the loose thread under the wound part… I am eyeing how you’re using the two notches and might switch up. That looks much better and more secure.
I do store all my bobbins in a fishing tackle box tray, they fit really good and the trays have dividers so I can keep them in order.
Didn’t know this movie was out! Going to see it tomorrow before it’s gone.