How to exit Assembler back to Applesoft Basic on Apple II GS
You can just type Ctrl-C.
(Or Ctrl-B if you don't care about wiping any Applesoft program in memory. Also, ">" is the Integer Basic prompt. The monitor prompt is "*".)
Type 3D0G at the assembler prompt. This will cause the computer to goto/execute the instructions starting at memory address 3D0 Hex/976 decimal, which is the address for the Applesoft Basic interpreter.