Which is the most clever way of keeping both (“stable” and “cutting edge”) app versions and keep them updated?
Duplicate the app in the application folder. Call one of it “Glyphs Stable” or “Glyphs Cutting Edge”. Then start the one you like to be cutting edge and enable “show cutting edge version”. The only thing you need to pay attention to is to not update when you are in the stable version. Maybe deactivating “cutting edge versions” most of the time to be sure.
Thanks. Is it important to keep them inside the Applications folder root? (I have them in a subfolder, with type-related apps).
Subfolders are fine.