Aber die Feinjustierung/-abstimmung sind doch die small adjustments, nicht das dial-in, oder? Schon mal nachgeschaut, ob man in der deutschen Baristawelt vielleicht einfach "Dial-in" verwendet, Poison13?

A Guide To Dialling In Espresso - Perfect Daily Grind

FWIW, aus dem Link in #5 :

 ... What Is Dialling In?

... The phrase “dialling in” is used to describe the process of making espresso taste as delicious as possible. Essentially, you are looking to extract the right amount of soluble flavour from the coffee using the right amount of water.

In order to achieve this, you must change the parameters of the espresso. The three main parameters are the dose, yield and brew time, all of which have a massive impact on flavour.

When dialling in, you should only adjust one parameter at a time, otherwise you can easily lose track of which has affected the espresso’s flavour in a certain way.

Extraction levels are also important when it comes to dialling in. When not enough coffee extracts into the water – under-extraction – the espresso often takes on a sour taste and a viscous consistency. If too much coffee is extracted, however – over-extraction – then the espresso can taste dry, bitter, or burnt. ...

Habe gerade den Link in #5 durchgeschaut und ziehe meine #6 zurück - mit "dial in" ist hier m.E. tatsächlich die gesamte Zubereitung gemeint, siehe z.B. die Anleitung hier.

I know of a Barista who operated her own private coffee shop and made excellent espresso and other coffee drinks. She insisted on using only a particular blend and roast from a small coffee roaster in Hamburg, In addition to adjusting her machine to the parameters listed in #5 at the start of each day (the "dialing in"), she also had to factor in the particular weather conditions of the day. If the weather changed drastically, such as a thunderstorm arising, she would have to make adjustments for that during the day.

OT, from #5:

"Stay hydrated. Dialling in often involves tasting a lot of espresso in a short period of time, which can affect your palate and obscure the more subtle flavours of each individual espresso. It can also mean you end up being over-caffeinated, which can cause dizziness, shaking, shortness of breath, and an increased heart rate. You should drink plenty of water before, during and after the entire process."

For some of us, tasting a lot of espresso wouldn't be the worst fate. However, if you are really just tasting it, you would rarely need to drink more than a sip from each attempt, which I would think would make getting over-caffeinated rather difficult.

Interesting that M-W implies that this meaning originates from motor racing,

Where did this come from? Early usage of dialed in applied the term to the tuning of automobile engines. 

but makes no mention of the radio, which required tuning by means of a dial...