Use the "Reuse post" option to save time on repeating assignments.
Use + Create > Topic to organize assignments into units. To make sure I give you the best advice, are you trying to: Post an announcement for all students? Create a graded assignment with a Google Doc? Create a poll/question ? google classroom
Let me know which one, and I can give you more specific steps. Reuse a post - Computer - Classroom Help Use the "Reuse post" option to save time