It’s one of fishing’s mysteries. Wind leader nice and tight on each of those spools in your spool container. Stick the container in your bag and leave it there undisturbed for a week. Then return to find that leader has not only worked itself loose on each spool but has somehow seeped out of the spool bag, leaving the latter looking like it’s been immersed in a spider’s web.
By that stage, the first two feet of leader on each spool are so kinked and coiled as to be good only for early retirement.
This home-made gizmo, while employed on tying thread in this demo, looks like it could be easily adapted to bring that leader nightmare to a close…