Product Categories. By ID

On the supplier form first page, in the "General buttons" section, there is a button "Use category ID":

If you enable it, then the "Category and Margin" tab can be left blank.

But in the price list, in the category columns should be your site category_id:

The category ID can be found in the database in the category_description table and in the admin when you open a category for edit, the ID is in the page URL.:

Settings

In the "Category" field, it is enough to enter the numbers of these columns, and the plugin will distribute the products into categories when is set to adding mode.

or

This method has one drawback - the product images will be uploaded to one folder - image/catalog/photo

Which can slow down the site.

This happens because the "Category and Margin" tab was not filled with categories and folders for product images:

and the plugin doesn't know where to upload product images for these categories. By default, the preset folder is used -image/catalog/photo.

Adding many images to one folder is not a good practice

How to fix it?

You have two options in "Tools" tab:

In the first case, the plugin will evenly divide all the images in the photo folder into 10 sub-folders, and in the second case, each of these sub-folders will be divided into another 10 sub-sub-folders.

Thus, all images will be distributed into 100 folders.