As of version 1.1.2, multiple categories can be selected using the cat_id attribute. Simply provide a comma separated string of the category ID’s to include. Use a negative ID to omit multiple categories.
For example to include a yearly archive of posts with both the categories of ‘Archive-Pro-Matic’ (ID 55) and ‘collapse-pro-matic’ (ID 43) the shortcode would be:
[archives type="yearly" cat_id="55,43"]
Note: Currently the title of the archive page will display only the first category. A solution to display multiple titles is in the works. Multiple category titles will now display on the archive page.