As you have noted there is a vast array of possible Psets described by BuildingSmart. I can only find these 9 Psets so far.
All these standard BS psets are 'baked' into BB.
Certain psets are tied to certain IfcClasses. That is, in the BlenderUI, they only show up in the UI when you have an object/type of the correct class selected.
For example, if you wanted to use Pset_ElectricalDeviceCommon you'd have to create and select either a IfcDistributionElement or IfcDistributionElementType

Some psets are more 'universal' and can be applied to multiple classes that are subtypes of IfcElements.

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How do you 'find' which pset are available? There might be an easier way, but I just like using google with the following search syntax.
voltage site:https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/
Is basically searching for voltage
in the IFC4 spec.
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Searching the IFC 4.3.x spec is easier, as there's a search field on the website.
https://ifc43-docs.standards.buildingsmart.org/
