This feature is only available in classic Groups, and it’s planned for deprecation with the switch to new Groups.
For groups you own or manage, you can set an option to allow users to make changes to their messages after posting them.
- Sign in to Google Groups.
- Click My groups.
- Click the name of a group.
- At the top right, click Manage group.
- On the left, click PermissionsModeration permissions.
- Next to Edit Own Posts, click the displayed optionchoose whether to allow group owners, group managers, or all group members to edit their own posts.
- Click Save.