[robocat]

That's like visual puns, and is limited to whatever symbols seemed important to the developer at the time.

How do you discover how to type ß, °, «, ‡ etc?

Android's gboard uses phonetics (long press [s] key for ß), symbolic similarity (long press [*] key for ‡) and visual similarity (long press [<] key for «) which is guessable for some symbols, but isn't discoverable for others (you can search for emoji by name, but not symbols).

[macintux]

The Mac has had, as a standard feature for decades, an on-screen keyboard to allow you to explore the results of different key combinations. It’s a great tool.

[macintux]

I should note that, alongside it, is a useful search tool that allows you to find the character you’re looking for if you’d rather just search and don’t care to learn the key combination (if there is one).

[cpach]

Cool! Where do I find it?

[macintux]

In Mojave, and it’s pretty similar across versions IIRC: open keyboard preferences in system settings and check the “Show keyboard and emoji viewers in menu bar” box.

That will replace the language flag icon in your top bar with an odd icon with the command key embedded.

The second option in that menu is the keyboard viewer. You can show that and drag on a corner to make it as large as you want. Dynamically changes the keyboard as you hold down modifier keys.

[kps]

It's easy on the Mac to have a custom or purpose-built keyboard layout that makes sense for the user or context. It's a little harder with X (mostly due to uncoöperative DEs) but still doable.

[kps]

Self-reply for Kwpolska: Adding layouts to /usr/share/X11/xkb/symbols/ is straightforward (but is necessarily system-wide, and requires root), and I do that. However, for the popular desktop environments, it's like pulling teeth to have that layout treated as first-class with respect to switching and settings.

(On MacOS, putting a .layout file in ~/Library/Keyboard\ Layouts is enough.)

[Kwpolska]

I've hacked /usr/share/X11/xkb/symbols/xx files to have custom keyboard layouts, DEs are not able to mess with it.