Thanks for the suggestion!
Actually I'm thinking now to link my Main Index template to an external file and keeping two copies of index.html in my external editor on my computer (one as backup and one as test). So I can make changes to index.html, upload the changes to the external file, which will auto rebuild the index.html (if I understand the "Link template to external file" feature), if I do not like it I can simply upload the back-up index.html. Once I have an acceptable new version I can then update the backup on my computer. I should be able to do this with all templates.
I have a MT Dreamweaver extension now so this should be as easy as pie.