This feature requires an ArtStation Pro account.
When creating or editing a project, you can select the visibility of the project. You can select whether to show it on ArtStation.com, your website, both, or none.
This is useful for situations where you want to publish work that may not be completely appropriate in the ArtStation community section - e.g. photography. Alternatively, you can use the Pages feature to post work that isn't to be on the community.
To hide a project. Simply uncheck both boxes. It won't show up on your website or on ArtStation. People with the URL will still be able to view it but it won't be listed on your portfolio. This is useful for when you want to show someone a project in private.