I use KDE, and I put a sticky note widget on my top bar, so when you click it, it drops down (and then disappears when you click off of it). Whatever is on it is saved between sessions.

Works great for this kind of thing.

Edit: I also put a webbrowser widget up there that points to this handy site: https://linuxcommandlibrary.com/

Same deal, click the icon and the site drops down.