I have a Blogger blog whose layout and theme I’ve tweaked using the Blogger-provided tools. I’d like to copy this design to another Blogger blog and then tweak it further, again using the provided tools (i.e., without having to edit the CSS or HTML manually). Is this possible, and if so, how would I go about it?
There are two Blogger template styles - old (original) & new (makes it easier to add widgets). Assuming both the blogs use the same layout style, you can copy the template from the first blog to the second.
From the Blogger Dashboard, you can click on the Template or Design tab & copy the HTML of the first blog over the second through the Edit HTML tab. As you can preview the changes before you save the Template, you can confirm if the tweaked changes (which may have dependencies) work fine in the second without losing anything. You can also backup the template on the second blog prior to changing it.
Blogger itself provides templates that lets you change the style while keeping the content intact.
There is no way to do this, without using the Edit Template function.
Even if you copy the template code from one blog to another, it only works properly if the widgets are added in exactly the same order (so that HTML2 on one blog is the same as HTML2 on the other) - and even then, the widget settings need to be manually re-created.