You can present a scene on your computer without uploading the scene. Scenes that have not been uploaded cannot be accessed on the Internet.
If you would like to upload a confidential scene and share it privately with a link, you can create an obfuscated scene name by appending random characters to it (for example 'building-grymgutunsav'). Such a link gives a reasonable level of confidentiality if it is shared with care.
Links to uploaded scenes are never shared on the Shapespark homepage, social media, or by any other means without the author's consent.