If you choose to start a module, but then change your mind and decide you want to work on something else, you can abandon that module and come back to it later.
To do this you need to click the "Stop" button on the module page:
This will open a new window, click the 'I'd like to pick another module instead' option. Once you click 'Yes' you'll be taken back to your timeline and you'll be able to pick another module to work on.
