Another useful feature is some part of my environment (I've used it in Gnome 3 on both Fedora and Arch, but it doesn't work in RHEL; I'm honestly not sure what part of my stack is providing the feature) lets me pres Ctrl+Shift+U and enter arbitrary unicode. I've memorized the hexadecimal representation for a few common symbols and can enter them into basically any text field.
> I'm honestly not sure what part of my stack is providing the feature
It's Gtk. Gtk applications on Windows and macOS also use the same keybind to enter characters by Unicode code point. (It's kind of a pain if you use a lot of cross-platform applications, because you end up having to think a bit about what GUI toolkit the application is using before you can type a special character. “Does this one do the native thing or something else?”)
