Best translated as ‘non-forcing’ rather than ‘actionless action’ or ‘non-doing’.
Action that arises, unbidden, out of one’s ontological or phenomenological parity with Nature. Effortless, non-forced, non-rigid doing, like the orbital revolutions of planets or perhaps the tropisms of plants.
“The art of sailing rather than the art of rowing.”
[see also: Csíkszentmihályi’s ‘flow’]