When items are collapsed their children are not injected in the webpage structure, so you can have thousands of hidden items and only the visible will have any impact while document is loaded. I have few huge documents with more than 1000 items (including Propædia, an outline of all possible human knowledge ), and dozens of smaller ones. It doesn’t matter for loading time or in any other moment which one I’m working on, and also on which platform. Even Android app is just a wrapper for web app. Use it in whatever way you like 
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