When students submit a post to an input element, they always have the option to edit or delete the post. You as teacher can edit or delete any student post, with the exception of drag-and-drop element posts.

Click the thumbnail of the post you want to edit or delete. From the drop-down menu that appears, choose the desired action.

note that a post submitted on behalf of a small group can be edited by any member of the small group.
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Also, The discussion wall also enables you to change the share settings of a specific post or the entire instance of a discussion wall.