Why delete files in actions?
Deleting files from an action keeps records clear and updated. As an action progresses, the files attached to it can quickly become outdated. Someone may have uploaded the wrong file, added a duplicate, or attached an earlier version that's since been replaced or updated. Deleting files directly from an action's activity timeline ensures the record reflects the current state of the action.Over time, keeping files accurate makes it easier for your team to review, close out, and report on actions confidently.

By default, users with "Override permissions: Manage all data" permissionhave full access to actions in your organization. This means they can delete files uploaded by other users in the organization.
Deleting is irreversible, and we cannot restore permanently deleted items. Confirmation is always required before any deletion, so be sure you're not accidentally deleting the wrong item.
Delete a file in an action
Select
Actions in the sidebar or select it in
More .
Select between
List ,
Calendar , or
Board on the upper-right of the page to view the actions.
Select an action.
Click Activity on the upper-right of the page.
Click the file to preview.
Clickon the upper-right of the media preview.
In the pop-up window, click Delete .

You can only delete files on the web app. On the mobile app, you can only see who deleted a file and when in the activity timeline.