Should work in 1.13+, though I've only tested on 1.15.2. Stores over half a million items per silo, so 1mil items per full slice.
My Discord: https://discord.gg/zEnfMVJqe6
World download (1.15.2): https://www.mediafire.com/file/ufaybt0eq3zcwuw/storage.zip/file
Something I forgot to mention is the shulker box input system. In the world download I just have a single double chest feeding into a bunch of hoppers. With carpet shulker stacking, this will last for quite a while, but in vanilla you'll probably want to add more chests above. You could also hook up a chest inside the room to an item elevator but I didn't do that since it's easier to just fill it up and forget about it for a few months.
XeKr's Wild Joker resource pack: https://www.curseforge.com/minecraft/texture-packs/wild-joker-redstone-display
