..... continuous, flashing, pulsing, strobing … special patterns, etc., just looking for what road regulation (e.g StVZO) prescribe, or simply recommend, as far as rear lights are concerned. In other words what’s the minimum power emission in terms of light, what are the recommended/admitted/legal patterns to improve perception and at the same time to limit collateral distresses such as dazzling or other annoying disturbances ?
I’ve been trying to go through German StVZO but I found the subject terribly complicate and so far unpracticable.
From this point of view I do prefer the pretty essential Italian prescription that requires “0.05 candela within ±10 degrees either vertically and horizontally”.
But what about flashing, pulsing, etc. ? Are they legal ? .. and which of them are legal and which ones are not ?

StVZO allows only constant lights. No pulsing, no flashing, no special patterns. It is believed that pulsing makes it more difficult to estimate the distance to the light.

To me 10 degrees of visibility from the side seems not enough for StVZO, but I can't tell the correct numbers.

Bicycle lights are only allowed to be used or sold in germany, if they have passed an examination by the authorities. Fines for sellers are significant.

I would'nt be too much concerned when I would be planning a bicycle tour passing Germany as foreigner (e.g. Italian). In that case any light will be appreciated if it can be seen and does not disturb others. I.e., if you plan to make a bicycle tour in Germany, you should not worry too much - at least, that would be my recommendation.

... well, actually my concern is not whether to be worried or not worried at all if I have to cycle in Germany; I did it many times and, believe me, I've been always feeling much more confortable cycling over there than in Italy.
My point, so far, is now more technical: what does StVZO says about rear lights flashing, pulsing or, even worse, strobing.
Nowadays I can see cyclists using any type of lights but I wouldn't be much sure that they are totally legal.

As was already mentioned, the strobing and flashing is not according to the StVZO. And as you also have realized correctly, nevertheless, Germans are using such lights. In the German part of this forum, recently, there was a discussion about this. Some of our forum members find the flashing annoying. Some others - like me - do not really care. I myself use a "regular" rear light according to StVZO. Usually, police will not complain about a flashing light, since they are in most cases happy to see a light at all . More complicated would the situation be in case of accident during night time. Insurances will try to fight claims by any means and if lights were not according to rules, there might at least a reduction of compensation payments be enforced.

Buying a head or rear light in a German bicycle shop will in practically all cases mean that you will receive a light according StVZO. EBay or other internet recources will also easily give access to Chinese no-name brands, which do not have the required approval mark (waveline with K + number). This is against the law if the seller is not private. Police nevertheless officially can tolerate such lights.

A good overview is given in Wikipedia, however, for German regulations of course in German (see HERE)).

Very clear, thank you a lot.

... however, formally legal, partially legal or not legal at all, my personal approach is to use, as I always did, a continuous light but, under very critical visibility conditions such as during heavy rains or in tunnels, I do prefer to activate some intermittent flashing mode.
Perhaps it's a little bit annoying but, IMO, the car or truck driver perception that just a few meters ahead there is a cyclist is definitely much better.

As others mentioned above it is much harder to estimate distance and relative velocity to a flashing light that to a constant one. From my perspective the best rear lights shine from a bigger area instead just from a single (LED-)spot. My favorite is the Philips Lumiring, but unfortunately Philips canceled their bike lights production. However, the German brand Bumm uses the same technology in some lights and advertices it with "Line Tec".

There is a huge difference between detecting an object and identifying an object. Flashing, annoying lights make it easy to detect an object, but it is almost impossible to identify it. Recently I almost crashed a dog, which had a flashing collar. I detected the "object" from quite a far distance, but mixed it up with a bike rear light. However, I only identified it as a dog, when I was just starting to overtake and I would have had crashed the dog, if it had decided to cross the street, just when I was passing. (Since I expeced a bike, which is not able to go left/right instantly.)

From my perspective, detecting a bike light with a working rear light, is not a big issue. Identifying it as bike is more complicated and estimating its exact position and speed, is a security relevant issue, which is much more difficult with flashing lights.

I don`t know the technical specifications for StVO-approved rear lights in detail. However, this is not needed for the consumer, since any approved bike light has to have a specific number "K~~XXXXXX" on the product and in Germany any light sold as bike light has to have this certification. So the consumer does not need to take care on that issue when shopping a light - all leagally sold bike lights are StVO-approved.