The number one & a must-have skill of a manager, not the one who has this title but the one who can actually manage, is
But many people think that "communicability" means "being friendly". In fact, there are many people who think "This person does not look friendly, he/she does not make me feel comfortable, that is why I cannot work with that person". I would not call such a person "a professional".
Communicability means an ability to clarify the thoughts of others and to deliver clearly your own thoughts. Communicability has components, elements.
For a manager, an expert professional with a strong personality is an asset, for a clerk - an annoyance, or even a threat.
Recently I failed a job interview. I recorded my own video - my reconstruction of the interview, based on the fact that during the interview I used at least 80 % of the prepared material. Here is a document prepared for this interview with some comments on it (I was able to communicate at least 80 % of it), i.e. prepared statements I wanted to present, as well as my professional recommendations on how to improve management (I emailed this document to the interviewers, and I expect that people who will use those recommendation would clearly specify their source).
At the end of the interview I was asked what was the biggest challenge in my life I had to overcome. For me it was no brainier - I had to drop a good career and move to a different country with no money, network, and language and then, starting from a janitor I became a very good teacher. When I said all that the next question was "How did you do it? What is your secret?" A person wanted that I would explained "a secret of how to succeed in your life". Writers have books about it, motivational speakers spend hours on it (and make good money of it) and the interviewer wanted to learn if from me for a couple of minutes. Of course, I failed.
This post was meant as an Appendix to this post, but since it turned out to be too large, I made it into a separate piece.