Hey there, there are indeed two workarounds to achieve this quite easily:
For Sitejet Studio:
- Duplicate the website
- Move the domain to the duplicated website
- Publish it
- Make changes to the original website (do not delete the content, like pictures, as they are referenced)
- When the website is done, just move the domain back
- Publish the “new” website with the changes
Or, you could just set up the websites you like to display and build the others in the background, not referenced or indexed. Once the website is done, you can just set them visible. Like described here: Under Construction Page
Hope that helps!