german keyboard layouts (QWERTZ), where the tilde originally was absent.
Are you sure? The tilde was available at least on all PC/AT keyboards I've ever owned since the 1980s.
Meanwhile it is on our keycaps, but I'm not sure about its "canonical" location
~ is usually (DOS, OS/2, Windows, Linux, *BSD) mapped to [AltGr] + [+*]. Macs, typewriters and home computers may be different.
See also https://en.wikipedia.org/wiki/German_keyboard_layout.
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)