Just in case anyone comes across this thread looking for a way to create an archives page without using a child theme or plugin or anything else, I just came up with a super easy solution using the new Elements module in GP 1.7.
1. Create a new page in WordPress (e.g. /archives/).
2. Add a new GP “hook” element.
3. Make it something like…
<h2>Archives By Category:</h2>
<ul>
<?php wp_list_categories( 'sort_column=name&title_li=' ); ?>
</ul>
<h2>Archives by Month:</h2>
<ul>
<?php wp_get_archives('type=monthly'); ?>
</ul>
<h2>Recent Posts:</h2>
<ul>
<?php wp_get_archives( 'type=postbypost&limit=100' ); ?>
</ul>
4. Set the hook location to after_entry_header.
5. Check “Execute PHP”
6. Set the display rule to “Page” and select the /archives/ page you made in step 1.
7. Save/publish.
Loving this new Elements functionality, by the way.