You need to do the following:
Go to your Extension Settings
Go to the Engagement section
Turn on the Enable Airtable comments on child forms toggle.
The Comments button is available in the three-dot menu in the header of the child form, right next to the close button. You can view or add comments from here.
You can only add comments when your portal uses a login. This means that users of the Shared View extension can only view, but not add comments.
💡Note
This feature also works with the form. When the login feature is enabled, the first login field will show up as a prefix of the comment by default. When you are editing a record using a form, the primary field of the table that your form is editing will show up as the prefix. You can change the commenter name using by defining the appropriate field in the Engagement section of your extension's settings.