Hello! Maybe try doing an enrichment, adding a new field and putting something together in the expression editor like:
Case(When(<field1> = NULL, 0),Else(1) ) + Case(When(<field2> = NULL, 0),Else(1) ) + Case(When(<field3> = NULL, 0),Else(1) ) + Case(When(<field4> = NULL, 0),Else(1) )
Each of the : Case(When(<field1> = NULL, 0),Else(1) ) parts just checks to see if your specific field is empty or not, then returns 0/1 depending on if it is. After that, it'll sum the numbers together and you get your count of how many of the product fields are filled/not. Just make sure you update each of the <field1/2/3> parts to be your specific fields.