I have had this problem over many versions of SolidWorks... but I am currently on SW2025-SP2.  I have downloaded a SolidWorks part file online from a large parts supplier.  It's a fairly simple part.  It has only 1 "default" configuration, but literally over 1000 display states... most of which (all but one?) are unnecessary and useless.  But when I try to delete the unused display states, it TAKES FOREVER when I first start out... literally 30 seconds to a minute PER display state.  As the total remaining number of display states dwindles, this time speeds up greatly.  But, why - in the world of GHz speed computers, and the highly advance capabilities of SolidWorks - would deleting something as insignificant as display states take more than say... 3.05 seconds, regardless of how many there were to start with?