For this part of the setup to upload sketches to the BiBoard, I'm having trouble finding the location of the sdkconfig.h file. I'm on a Mac, and have downloaded the 1.8.19 version of the Arduino IDE. I've been able to configure the environment as detailed in section 3.2.1 in the documentation. I see that there is a sdkconfig.h file in the OpenCatESP32 repository, but I assume this isn't the file that needs to be modified, as it already has this line at the end of the file.
Which version of the esp32 library do you use?
/Users/{yourUserName}/Library/Arduino15/packages/esp32/hardware/esp32/2.0.12/tools/sdk/esp32/qio_qspi
The Library is a hidden directory; you can use Shift+Cmd+. to show it.