How much to tip at a restaurant in Germany?

I was kind of wondering about this. Back in the 80s and 90s, I was in the service industry and there was a conceit that “Europeans don’t tip because it is not done in Europe.” Of course, none of us vetted that information, and it was probably an oft-retold word-of-mouth holdover from perhaps 20-30 years before.

About 15 years ago, I picked up a “do’s and don’ts” book for international travelers. It turns out – if that book was generally accurate – that tipping something for various services in most European countries was by then very much expected. Almost invariably less than the 15%-20% recommended in the U.S., but still … tips seemed to have become an accepted thing in much of Europe by ~2000.

Anecdotally: it seems, though, that service personnel in Europe (very generally) are somewhat culturally (right word?) constrained from making too big a deal about NOT getting tipped any one time … like it comes off as gauche and whiney, even to fellow service staff.

In contrast, if an American server gets stiffed in a restaurant, that server will at minimum make a big deal about it with their immediate coworkers, and will receive much sympathy.

I live in Germany 10% - 15% is a good figure give more if you like.

I’m the OP checking back in, folks. Enjoyed my vacation.

And I would agree that customs appear to be in flux:
One restaurant handed me the bill with the words “tip not included”. Another one printed “tip not included, but is voluntary”. (in English) . So I felt guilty, and not wanting to look like the Ugly American, I told the waitress to round the price up a few Euros.

Once, in a pub-type place: Unprompted, I told a nice waitress who spoke fluent English (a thing not to be expected) to take 15 Euros for a 13 euro bill. She seemed genuinely thankful, and maybe a bit surprised.
So out of a dozen meals, I tipped 3 times.

Almost everywhere took credit cards. Every time, they handed me the card-reader machine to type in my PIN code.
But they often handed me the bill first, apparently expecting cash. Only after I took out my credit card, they walked back to the desk to bring the card reader.