MG-Picker Studio uses Qt way to store its configurations for the Maya plugin and Standalone versions. It is in different places on different OS platforms. The unified way to query it is using QT API, with any PySide2 environment, you can query it by executing the code below:
from PySide2 import QtCore
dir = QtCore.QStandardPaths.writableLocation(QtCore.QStandardPaths.GenericDataLocation)
print("MGPicker Studio stores user config in: {}/MGLAND/MG-PickerStudio".format(dir))
Switch to the PyQt code by changing the import statement if you need to.
As a reference, on Linux, it is usually like
/home/users/yourUserName/.local/share/MGLAND/MG-PickerStudio
on Windows:
C:/Users/yourUserName/AppData/Local/MGLAND/MG-PickerStudio
on MacOS:
/Users/yourUserName/Library/Application Support/MGLAND/MG-PickerStudio
