You can add this Action selecting it as other standard actions from Form > Content > Actions After Submit > Add Action.
Preview in Editor
Let you display the result message in Editor Preview without the need to submit the Form.
This preview will be visible only in editor mode.
Here you can write your own custom message, you can place Dynamic data from submitted form fields using the placeholder [form:field_custom_id]
If you use the Dynamic Tags Template on this field you can use an Elementor Template instead the Text produced by the Wysiwyg
Remove default icon
Prevent the default icon added by Elementor
The message will appear as a Toast notification on a corner of the screen
Add a simple button on the angle of the message, so user can hide it.
Hide Form after submit
The form will disappear and will remain only the message
If you enable this action you can find a dedicated section in Style Tab with common style controls.