Cross-selling is indeed a proven sales method to sell more to your customers who have already bought at least once on your store.
Store Commander allows you to perform this marketing operation easily and quickly.
In this example, we will send a discount code for 'Belts' category to all your customers who bought an article in the 'Trousers' category.
Display the products in category 'Trousers' and select them all
Display the 'Clients' grid from the Properties panel
In this grid, you can see the list of customers who bought one or more of the selected products
Now click on the Quick Export icon on the toolbar to get this customers list onto a spreadsheet.
Refer to this article for further details on the Quick Export option.
You can now use this list with your usual mass-mailing tool to send the PROMO code on all articles in category 'Belts' to these customers.