There is a trick I use when I am updating theme demo site. I’ve copied the site in the same account. I set it to use a temporary Weebly free domain. I can complete the customization and changes there. I can also publish the site to test without affecting my live site. Once I am complete, I will change the domain name so it will become my new site. The download side of this is you may need two paying sites while you are making the alteration. The good thing is you can test, publish and modify the site without fear of changing you live site.