(The image is from B4J but it's the same thing).
You can create your own configurations, each containing one or more conditional symbols (words), separated by commas.
You can also add symbols to the default configuration named... "Default".
For example, I could add to "Default": ForMeOnly.
At runtime, I would have the symbols of the configuration I selected; in the example, "Default", I have not created a new configuration, and I could write:
#IF ForMeOnly
'''
#ELSE
'''
#END IF
The "Default" configuration already contains "DEBUG" and "RELEASE" although they are not visible, so I could use combinations of the 3 words contained in the configuration named "Default".
It is not "True" or "False", it is:
#IF (the selected configuration contains) [one of the symbols]