What are the steps to convert a simple product to a variable product using the CSV importer

1. Export the simple product you want to convert to a variable product using the built-in WooCommerce CSV exporter on the All Products page[1].

2. Open the exported CSV file and add new rows for each variation you want to create. Leave the original simple product row in place[1].

3. Add 4 new columns after the last column in the CSV with the following headings[1]:
- attribute:size - defines the values of the variations
- attribute_data:size - defines the position, visibility and if the attribute is used for variations
- attribute_default:size - sets the default attribute value
- meta:attribute_size - maps the variation values

4. Fill in the attribute and variation data in the new columns for each variation row. Leave the original simple product row blank for these new columns[1][2].

5. Save the updated CSV file with the new variation data.

6. In WooCommerce, go to the Import page and select the updated CSV file[1].

7. Map the CSV columns to the corresponding WooCommerce product fields, making sure to map the variation columns correctly[1][3].

8. Set the product type to "Variable product"[3].

9. Configure any other import settings and run the import[1][3].

10. Review the imported variable product with its variations in the WooCommerce product list[3].

The key steps are exporting the simple product, adding variation data to the CSV, mapping the variation columns correctly during import, and setting the product type to variable. This allows converting an existing simple product to a variable product with variations.