Does this plugin support attribute import CSV functionality?
Yes, for this you need to open the Variation Master > Import/Export Tab.
From this page you can download a CSV file for all available WooCommerce variations and after editing the file by providing the gallery image URLs separated by “|” press the “Browse” button and navigate to the modified file location and press “Import” button, the gallery images for each variation will be uploaded, make sure you enable the “Variation Wise Gallery” from general settings of variation master.