When saving a screenshot from the iOS Simulator, the screenshots are saved to the Desktop
After taking a few, my Desktop is quickly polluted with screen shots that don\'
Xcode 9 adds behavior for setting a custom directory for iOS Simulator screenshots.
Press ⌥⌘S or Hold the ⌥ Option key and select the menu item:
File > New Screen Shot...
This presents a file "Save As..." dialog. Note the new checkbox on the dialog:
Use this as the default location
Check that checkbox to change the default directory for ⌘S iOS Simulator screenshots.