I just wanted to point out that "Cognitive Complexity" [1] was not invented by SonarSource, it is an academic principle created in the 1950s and has more to do with psychology than computer science. Computer science has over-simplified the term to mean "hey there's a lot of stuff to remember this is hard".
Psychology tends to have a wider scope of thought and research put into it [2] [3]. For example, one way it's used is not to measure how complex something is, but how capable one particular person is at understanding complex things, versus a different human [4]. This can affect everything from leadership decisions [5] to belief in climate change [6].
I point this out because all too often Engineers hyper-focus on technical details and forget to step back and consider a wider array of factors and impacts - which, ironically, is what cognitive complexity is all about. It's the ability of a person to think about more things in a deeper way. Basically, cognitive complexity is a way to talk about not just things, but people.
We also have a tendency as Engineers to try to treat everyone and everything as a blob. We have to design our language in X way, because all people supposedly work in the same way, or think the same way. Or we have to manage our code in a certain way, because all the team members are assumed to work better that way (usually in whatever way is either easier or simpler).
One thing I wish people would take away from this, is that not only is cognitive complexity actually useful (it describes how language is able to work at all), but some people are better at it than others. So "avoiding cognitive complexity" is, in many ways, a bad thing. It's like avoiding using language to convey ideas. Language and communication is hard, but you're reading this right now, aren't you? Would you rather a pictogram?
[1] https://en.wikipedia.org/wiki/Cognitive_complexity [2] https://www.jstor.org/stable/2785779 [3] https://pubmed.ncbi.nlm.nih.gov/11014712/ [4] https://testing123.education.mn.gov/cs/groups/educ/documents... [5] https://deepblue.lib.umich.edu/handle/2027.42/128994 [6] https://www.sciencedirect.com/science/article/abs/pii/S02724...