By default, the current version of WooCommerce Mix & Match Products extension (version 1.2.3) does not display a short description of Mix & Match Product contents on the product page.
I wrote a code snippet which can help, however, you’d need to modify several extension’s files, therefore, use it at your own risk!
And viola, we’ve got our descriptions in place:
If you have any follow-up questions, feel free to ask in comments.
Happy Mix & Matching! 🙂