After updating the plugin to version 2.1 WooCommerce Product Size Guide is compatible with Product CSV Import Suite
Using CSV you will be able to export the content of your size guide items and then open them using office software like Open Office or Microsoft Exel.
After opening the file you will be able to change the content of imported tables by (for example) attaching products to new categories.
Below you can check step-by-step instruction how to use this new feature from exporting product Size guide tables to importing them after adding your custom changes.
DOWNLOADING PRODUCT FILE
1.Go to WooCommerce > CSV Import Suite and in Export Products tab choose Export Products – this way you will get .csv file with all of the product information.

Exporting Size Guide content
2. Open the .csv file using office software you have installed on your computer.
3. Please find AO columnt with the meta:_ct_selectsizeguide here you will find which products ( you will find products name in first column ) are attached to which size guide (ID numbers in the meta:_ct_selectsizeguide)

AO column
ADDING SIZE GUIDE TO PRODUCT
To add size guide to product you need to get the Size Guide ID to do that please:
1. Go to the Size guides and choose the size guide you want to add by choosing Edit

Choose SG
2. In the SizeGuide slug you will find a number – this is the ID we are looking for!

Size Guide ID
3. Go back to the downloaded file and add the ID to the product you want to use this Size Guide and save the changes in the file.

Adding new ID
IMPORT CHANGES
1. The last step is Importing the files with your changes – Go to WooCommerce > CSV Import Suite and in Import Products tab choose Import Products
2. Choose the option Choose File and add the file with your changes

Adding the file
3. Hit the Upload file and import button and it is done!