I just hit a frustrating wall and figured out the solution, but it took me a while.
I tried changing the shortcut for “Text Editing > Show Invisibles” from its default (Alt+Shift+V) to Ctrl+Shift+* (the default shortcut that I’m used to for Word). The keyboard shortcut menu accepts the shortcut, doesn’t show any conflicts, and saves it after clicking “OK”. But nothing happens when I try that shortcut.
I finally tried manually typing in 8 instead of * into the shortcut recording and that worked. This was frustrating because every other keyboard shortcut interface I’ve used treats Ctrl+Shift+* and Ctrl+Shift+8 as the same thing. It’s not clear to me why Scrivener would automatically record and accept Ctrl+Shift+* (rather than 8) if the asterisk won’t function as a shortcut.
Anyway, if this is a bug, I hope the feedback helps. And if anyone else has this issue, try deleting the asterisk and typing 8 in the shortcut string.