You can find it by clicking the link at the line following File > Preferences > More preferences can be edited directly in the file. The Arduino IDE has a 'data folder' named Arduino15. How could I start a clean installation, i.e.If you manually installed one of those packages, then there is a bit more of a process to it, but they provide clear instructions. If you install ESP8266 core for Arduino or Arduino core for the ESP32 via Tools > Board > Boards Manager, it is automatically installed with the package.
How is the esptool to be installed? With some other software ?.