Thank you for the help! I have it mostly figured out I think. I am getting stuck on something, and thus can't really figure out anything beyond that point: I can get items to go into the storage fine, but I can't get them out. They are 'eaten' essentially--when I try to remove items, it empties the storage slot but doesn't give back any items. I don't know if Input Number isn't going to the variable properly for data storage or what the issue might be. I've worked on it all day to no avail, so I thought I'd come back here with that update. The variable on Input Number for the items in and items out should be the same, correct? Or should there be a separate variable for items in and one for items out? I don't think that's where it's stuck, but it's an idea. I think it's getting stuck on this bit here from what the debug menu said: (variable 454 is Deposited Item Quantity, so the Input Number; 416 is Selected Slot ID)
$gamePart.gainItem($dataItems[$gamevariables.value(416)], [$gameVariables.value(454)]);
Once I get past that point, I might end up with more questions, but right now that's where I'm stuck. Everything else to that point is working perfectly fine.
Editing to add: thank you for all your help, and I'll still keep all this info as a learning experience, but I found a plugin that does what I need in a way that better suits my game, so no worries on getting back to me with answers!