Suppose I want an external language cell in my Notebook. I press > at the beginning of the line. I get a little Python dingbat on the left for the Python code I might want to enter. But what if I don’t want to use Python? I want to use R or Julia or something else. If I want R code, for example, and an R dingbat, I have to scroll down every time I press > and click R. While there are harsher forms of oppression out there, it’s a bit of a nuisance where one has dozens of R cells. (Or Julia or anything but Python). Is there some option I can set or another thing I can do so that R is the default CellEvaluationLanguage for an ExternalLanguage style cell?
Just spelunking through the code (search the core stylesheet to see how the front end decides what language to use and then follow from there) I can see there is no documented user settable way to do this. You should file a suggestion with Wolfram Research to make this user settable here.
That being said, it looks like you can set something like
ExternalEvaluate`Private`$FElang = "Shell"
during a session and all subsequent external language cells will be of the “Shell” variety.