Hi all,
Thanks for your votes on this topic.

Version 8.5 has now reached public beta, which includes this feature: https://blog.whmcs.com/133713/whmcs-85-beta-now-available
The documentation for these new options has been published at https://docs.whmcs.com/Cross-selling_and_Product_Recommendations_In_WHMCS
Please join us during the pre-release testing period and provide your feedback in our dedicated beta community board: https://whmcs.community/forum/582-whmcs-85-beta-discussion-board/