I've checked the Shader Tree Methods and Shader Node Methods sections of the PoserPython manual and can't see any way to select a node or group of nodes.

I'm writing wacros to add useful node groups, and want to ensure that all the nodes I create are selected so that they can be easily repositioned by hand.

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).