Hello
How to properly remove micropython installed on Nano ESP32?
I would like to return to programming in the Arduino environment after testing micropython.
Hello @adatat_73. Should be as easy as a double-tap of the RESET button while the lights are fading. Your Nano should then slowly pulse a single color - that means it's ready for a new sketch!
I found the answer, checked - it works.
Reinstalling the C++ Arduino Bootloader
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The first step in reinstalling the Arduino Bootloader is to put the board into bootloader mode, as you did earlier.
Once it is in bootloader mode (B1=GND), you can open up the Arduino IDE. I recommend having either the Blink sketch or a blank sketch open, as whatever is in the IDE will be transferred to the Arduino when the bootloader is installed.
The IDE should see the connection to the Nano ESP32, but it will likely identify the board incorrectly. You’ll have to open the connection and change it to the Arduino Nano ESP32.
The next step is to go into the Tools menu and scroll to Programmer. Highlight it, and a second item called “Esptool” will appear. You need to select this if it isn’t already selected.
Finally, open the Sketch menu and select Upload Using Programmer. This will load the bootloader and the sketch you have in the IDE.
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Well, that works too! 
Thanks for getting back!