Hello,
References:
- https://processing.org/reference/selectFolder_.html
- Java.io.File Class in Java - GeeksforGeeks
- https://processing.github.io/processing-javadocs/core/processing/core/PApplet.html#selectFolder-java.lang.String-java.lang.String-java.io.File-
I was able to use the File datatype for file using this syntax for selectFolder():
selectFolder(prompt, callback, file)
And set the default path to c:\test:

:)