At any time, you can see all of the hidden widgets on a page by clicking the Unhide Elements() icon at the bottom of the left panel under SEO & Settings.
The Unhide Elements icon only displays if you have hidden elements in your site.
To unhide elements:
If you are using the unhide element feature and it does not reveal an image on your site, your image might need to be added and uploaded.
For more information on hiding elements see the Hide on Device section in Edit by device
Hidden content may still show in the code of the live site (after publishing/republishing). This is expected and due to the technology used. For detailed information see Why is content I have hidden showing in audits?