This option is available on Matching Column (Step 2) of Update & Export feed only. 
In Shopify, a product category is called a Product Taxonomy; you can find a full list of all product taxonomies in the lookup table here. (English)
There is a setting for this field which is:
1. Language
You can choose the language in the extra setting of the Product Category.
The feed file can have both the ID and the product as below and Stock Sync is able to update the product accordingly.
For other languages examples can see below:
For example,
If your feed file doesn't have any column as a product category and you want to apply all the product categories as Home Supplies for all your products. You can select the option Static and enter the value in the field.
For all feed that was created before 7th November 2022, Please do recreate the feed and add this field again since Shopify changed the field name.
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