As you build an S-Docs template, you'll likely want to generate a document using that template several times in order to see how each change you make appears in an actual generated document. You can streamline this process by using the Template Preview feature.
To use this feature, navigate to the Advanced Options tab of the template editor and find the Preview Settings section. This section has a single field titled Preview ID. When you fill in the Preview ID field with the ID of a test record, a button titled "Save & Preview" will appear at the top of this page. You can click this button to generate and view a test document for the Account record with the ID you provided.
When you click "Save & Preview", a new tab will open in which a document is generated and automatically opened for previewing. As soon as your document is opened for viewing, the corresponding S-Doc record and Attachment/File record (if applicable) that were created are deleted from Salesforce (unless the Template Format is DOCX). This saves you even more time since you won't need to worry about deleting all of the test documents generated throughout your template development process.