I would like to know the details (definition and default values) of built-in flow variables in each node, e.g. how to know which flow variable can be used in controlling "range matching" instead of "pattern matching" in Row Filter node? Any documentation of flow variables in each node?
no there is no documentation is available. The name of the flow variable option should be self explaining. However, there might be cases where it is more difficult to find.
Is there any node in particular I can help you with?