Hi,
thanks for your reply.
Indeed, the way I launch PyCharm seems to make a difference. I usually start PyCharm via JetBrain’s Toolbox (i.e., no shell terminal). Triggered by your question, I restarted PyCharm using the shell script generated by the Toolbox App (which is a very simple wrapper around open -a "/absolute/path/to/the/executable/pycharm" "$@") and this time SonarLint did find the node executable. I cannot be sure without further experiments whether it found the node installed by nvm or the one installed by brew as /usr/local/bin/node - but I assume it is the former because its installation directory appears first in my shell’s PATH.
However, I had assumed that SonarLint started via the Toolbox would at least find the executable in /usr/local/bin. Or that I can somehow explicitly point the plugin to the executable on my local machine. Using any properties from the server would obviously not make sense here and relying on PATH if the value of PATH is not easy to control depending on how PyCharm was started is less than ideal…
You mention the versions of SonarJS/SonarTS. It is my understanding that the version used locally depends on whatever is installed on the server, doesn’t it? I will ask the colleagues who operate the server whether they can upgrade the plugins. However, server-side upgrades usually need to be planned; there’s a reason why we have the Enterprise Edition. 
Cheers,
Christoph