@DJGummikuh
Not just the 1st, 2nd, 3rd, and 5th level of keyboard inputs - no you also have the Compose-key, and Ctrl-Shift-U.
Windows: Ctrl-Alt and a couple of special symbols is enough, I guess - but you need a numpad, otherwise you can only get your languages alphabet.
MacOS: Yes, you can enter any Hex-number, but you have to switch to the Unicode Hex-keyboard layout first, then press Option-Number to type that number, but please no more.
Typing on Linux: Best experience.