Use Comment on Collected to create a comment on all your previously collected items without the need of a For Each action.
For example, to comment on all deliverables attached to a project when a project invoice has been paid, you can use Comment on Collected to make an identical comment on all referenced deliverables.
Then add the Comment on Collected action.
Select the collected items you want to comment on from the In App dropdown menu and enter your comment in the Comment Body.
You can change the authentication in the options (opt), thus creating the the comment by an admin member.