To enable the sorting by WooCommerce attributes, go to WordPress Plugins, find Custom Product Order and click the settings link.
You will find the sorting type options on the bottom of the screen:
All the custom and global WooCommerce attributes will show up here.
Each attribute can have one of the following sorting options:
- Lowest to Highest (A-Z)
- Lowest to Highest (0-9)
- Highest to Lowest (Z-A)
- Highest to Lowest (9-0)
- Both (A-Z & Z-A)
- Both (0-9 & 9-0)
Once you select the sorting type for an attribute, the option will become available in the sorting dropdown and default order settings for products.