Adafruit really likes the Mu editor as being the best way to edit CircuitPython code. Mu works on multiple platforms and it has built-in functionality to work with Adafruit boards as well as micro:bit, PyGame, and Python 3.
In December, 2018, Jon Mayland posted a cheat sheet for using Mu in Python 3 Mode, Various menu items are listed and some keyboard shortcuts.
The sheet below is patterned after the Python 3 mode sheet but is tailored towards the CircuitPython mode in Mu. Mu in Adafruit CircuitPython Mode does not have debug features but it does have serial and REPL capability. Here is Adafruit's CircuitPython mode sheet and file links:
See the next page for the source files in PowerPoint.