Can I select a subset of pins in Google Earth and export the attached data to a csv file?

Assuming you're working in Google Earth Pro (desktop), not the new web/mobile version, you can select multiple placemarks/points by holding down the shift or ctrl button and clicking in the MyPlaces/list view to select more than one. Then you could drag them into a new folder, save that folder as a KML, and find a way to convert that to CSV. But since you're going to have to use some other software to do the CSV conversion anyway, might be worth using GIS software (QGIS, ArcGIS, etc.) to do the selection and export without having to go through KML. GIS software will also let you do much more sophisticated selections, like select by area, select by distance, select by attributes, etc.