To access Dev Mode, shift + click the Snap! logo at the top left corner of the editor and click on "Switch to dev mode." Dev Mode allows the morphs to be inspected and edited. Everywhere you right-click, a morphic context menu appears. There are extra primitives that only appear in Dev Mode.
The extra blocks are:
console log [] @delInput @addInput :: looks alert [ ] @delInput @addInput :: looks save [ v] as costume named [] :: looks play () Hz for () secs :: sound (message :: control) (processes :: sensing) (stack size :: sensing) (frames :: sensing) (yields :: sensing) (type of [] :: operators) ([ v] of [] :: operators) show table @list :: list