how do I delete an app from the organizer left menu
Delete the apps from Xcode Organiser by going to
~/Library/Developer/Xcode/Products
and deleting the folders from there.Close and reopen the Organiser.
You can go to Xcode > Window > Organizer, right click on an archive and click open in finder, then press Command + DPadUp to move up a folder and see all the archives. I had 120GB.
You need to remove the App's archive's from ~/Library/Developer/Xcode/Archives
along with ~/Library/Developer/Xcode/Products
to remove it from Xcode's Organizer completely.