Bags In bags

Create containers that go into your main bag that can hold multiple items of the same variety, that all adds up to the total maximum storage of that container and weight

Core concept
4 of one color firework takes 1 spot, so why take up 4 slots for 4 different colored fireworks when you can throw them all into a container that holds them all. If you can hold a total of 30 for item x or y, and they are both similar, you would be able to shove both into a box if x + y is less than or equal to 30

Personal twist (optional)
These boxes take 1 hand to hold, and are pretty much just small grass bags. I don’t think it should only be an attachment.