If you are talking about change some parameters. The config.ini file with the parameters value of your emulated device is located in "Drive":\"Android folder"\B4AEmulator\"Emulator device name" (in my case C:\Android\B4AEmulator\6in_Phone_Platform_28_default)
I looked there and that directory only contains the 3 default AVD sub-directories. I see that other AVDs I previously created are in "C:\Users\username\.android\avd\". I had seen these before but I think I missed the references to "image.sysdir.1=system-images\android-24\google_apis\x86_64\" in "config.ini". It appears that accessing AVDs via Android Studio is much better than accessing them through b4A. Having them in one place is also an advantage. The 3 default AVDs in the folder you mentioned are so "ancient" that they hardly seem worthwhile. But I am no expert. Thank you for your help.
in "C:\Users\username\.android\avd\" I have just 1 file "6in_Phone_Platform_28_default.ini" containing: