When adding variations for products, if you try to “Use Existing Products” and then attempt to search for an existing product to use, the search never returns any results.
CS Cart Store Builder Version 4.17.2.SP3
There was another post on the forum with the same issue and they said CS Cart support had to create a missing column in the products SQL table:
4.12.1 Adding Existing Products To Variation Displays No Products - General / General Questions - CS-Cart Forums