I was educated in Germany mainly in the 70s, in a middle-class family that did emphazise proper etiquette. From that education, I learned that is OK to use a toothpick at the table - but ONLY if you do it behind your napkin. Nobody is supposed to see anything but your napkin.

However, that was at a time when toothpicks were generally available from a dispenser at the table. Those dispensers have vanished since. I cannot recall any quality restaurant I visited in Europe during the last couple of years that had a toothpick dispenser. So... customs change - and a 50-year-old book might not be a good reference.

Today, I would not ask for a toothpick in a European restaurant - and thus would use none. If I happen to run across a table-side toothpick dispenser, I might still consider using it. After all, if the toothpick is offered in such a way, it should be reasonable to assume that it is OK to use, isn't it?