In Apple-conforming macOS applications the key combination Command-Control-Space bar opens what Apple calls the "Emoji & Symbols" keyboard. In an application with an editor pressing that keystroke combination opens the macOS keyboard containing multiple character sets, including math symbols and punctuation. Double clicking on a symbol in the macOS keyboard causes that character to be inserted at the cursor. I cannot make this work in RStudio, whereas, I can from any other editor application, such as, for example, vim, running concurrently on the machine. Is this feature present in RStudio, and if so, how do I access it? If not, why not? Why is this important? All sorts of raw data to be reduced with R contains special characters and symbols that may need to be searched, matched and parsed in R, such as the string trimming and parsing functions. Simple example: the degree, prime and double prime symbols present in latitude and longitude data.
Also curious, while Option key typing (e.g. Option-U then I for ï) works fine, holding a key for diacritic options results in an extra character before the desired one, e.g. hold-I then 5 returns iį instead of just į.
Solved! I am now keeping a bash terminal/vim instance open along with RStudio. vim for editing, so much superior to the editors in R or RStudio, and RStudio for run-time execution, plotting and package management. Edit in vim, save and then source in RStudio. It's a kludge that R/RStudio could solve by incorporating open-source vim in R console or the RStudio editor pane, but then again, so many software engineering workarounds are kludges meant to overcome some inherent platform deficiency. R is superior math functionality but some of its human interfaces are less than stellar.