I share my computer with other users which use KNIME as well. So when the other user starts KNIME and selects his workflow folder he receives following error: ERROR PythonExtensionPreferences Failed to read Python extension preference yml file at C:/Users/andi/Documents/Knime_Test/PythonNode/config.yml
My login is andi and I worked on Python Based User-Nodes
so you changed your KNIME Analytics Platform (specifically you point in the knime.ini, which should be in the folder of your KNIME Analytics Platform, to ...config.yml).
If you are not developing these nodes further, you could delete the corresponding line in knime.ini.
If you want to use these nodes still, I suggest one of the following two options:
Have different KNIME installations for different users on your computer.
Move the files of your developed nodes (PythonNode/config.yml and so on) to a folder which can also be accessed by the other users of your computer.