This is rad! I tend to find animation and motion design daunting; the step-by-step construction of the menu really helped me understand how something like this can be put together. Thanks for making this!
This seems... not true, as https://www.sqlite.org/appfileformat.html indicates it "automatically coordinates concurrent access to the same document from multiple threads and/or processes" (search for: "Concurrent Use By Multiple Processes").
In general: try tapping the dots at the top of the app, or tapping the app's icon in the dock.
For Mail specifically: there's an icon in the lower-right of the sidebar that looks like two squares, one on top of the other- try giving tapping that.
(It didn’t. At all. It’s an insanely wild ride.)