Thanks, that terminal app command suggestion was helpful in fixing a preview crash problem that I had.
There were two additional things that I had to do:
1 - if the simctl utility is not on your path (likely the default case), then point your terminal at: Applications/Xcode/Contents/Developer/usr/bin (you may need to unhide hidden folders and/or open the Xcode package), and do the command as: xcrcun ./simctl --set previews delete all
2 - the -set option actually requires a double dash: --set