Unused weapons and figures in a plastic box like the one you have pictured.
I have several shoebox size rubbermaid tubs marked for specific tanks ie; T-34, Panther etc.
All others go into a miscellaneous tub.
Photoetch kept separate in marked envelopes in a file cabinet.
For me it’s not an issue yet, I have some Hobbyzone organizers, one drawer US figures and accessories, one German figure drawer. US, German labled drawers for spare parts, only delicate stuff stays on a piece of sprue, one misc aircraft drawer, and a bunch of storage drawers, one drawer for detailing bits like grant line bolts, odd little detail stuff etc that I pick up on a whim. I’ll probably have to redo this system as I jump into those manufacturers that give a ton of extra parts. Maybe it sounds odd but it’s relaxing to empty the drawer and sort thru for an odd piece and I save everything cause you just never know.