You can save a TeacherMade assignment as a draft in Google Classroom. 

To get started, follow the usual steps for creating a TeacherMade assignment in Google. Classroom.

Select to deliver the assignment via Google Classroom, and you will move to Step 3 of creating the assignment. Selecting “Saved as Draft” will allow you to finish setting up the assignment later. 

When you have finished creating your assignment, you will now see this:

When you click “Go to Google Classroom,” you will be able to see the draft of the assignment under your classwork.