A way I see to a purge individual samples, mentioned in the https://forum.hise.audio/topic/64/fun-with-regex --> under "DYNAMICALLY PURGE INDIVIDUAL SAMPLES", is to use this method:

// Select samples Sampler.selectSounds(your_selections); // Unpurge the samples (22 = 'SampleState', 1 = Purged, 0 = Normal) Sampler.setSoundPropertyForSelection(22, 0);

That purges the samples, but how to select things based on groups? (RRgroups)

The only thing I can find on RRgroups is the setSortByRRGroup. But that one seems to perform an internal task for performance, not for me to retrieve the data for selecting. Hmm.