You have an option to suspend a form until you are ready to lodge it.

Create a form.

To track suspended forms -

Navigate to Dashboard , select "Completed". *if the form was suspended after sending for signing, select "To Lodge". 

Filter by Form Type.

Look for the clock symbol.

You will not able to lodge a tax return until it is unsuspended. (Manual press "Unsuspend" to proceed with lodgement).

Please note that it doesn't change ATO due date.