Press the green flag. When the custom drawing mode is activated, press space to turn the pen on or off.
After seeing @z20342 's drawing project 'How To Draw A StickMan' , I thought I could make an easier way to program the drawings. Activating all of the scripts in the 'draw' sprite and deactivating the script on the stage will make the project usable to create a custom drawing. The Dalek contains a few errors.