Feed Import Products ( Commerce ) and Products Category ( Node Page )
The following CSV template and Feed Import settings will import 1 Product Node with multiple Product Entities being referenced.

Step 1 - Creating The CSV

The following example provides the title and product_variation headers...

title: Mapped to the Node Title field in Feed Import

product_variation: Mapped to the Commerce Product Referenced field. Field limit should be greater then 1, so multiple entities can be imported.

title,product_variation

Product Example,"product_sku-1|product_sku-2"


Step 2 -Import Node

The "|" is used to create a unique entry using the Feeds Import Explode plugin.

The Feed Tamper product_variation field should have a single Plugin called Explode with the String separator set to "|". 

Essentially, the Feeds Tamper Module will prepare the column values into an array, so Drupal can handle the request all awesome like :)