Cardmarket has no native CSV bulk-import for listings. This free, third-party browser extension fills its "Enter multiple articles" form for you, straight from your Lumex Pro export.

The extension filling Cardmarket's bulk-entry form from an exported CSV.
After exporting your listings as CSV from Lumex Pro's Listing tab, the extension reads that file and types the rows — condition, language, price, quantity — directly into Cardmarket's "Enter multiple articles" form for the matching expansion, instead of you typing each card by hand.
Cardmarket doesn't offer a native way to bulk-upload a CSV of listings — every card normally has to be entered manually through their web form. This extension is the bridge between Lumex Pro's export and that form.
Lumex doesn't ship its own bulk-import extension yet — an integrated version is planned (#79). Until then, this community project is the recommended way to bulk-list on Cardmarket.
Community project by PedroPerpetua (cardmarket-bulk-import on GitHub), not operated or maintained by Lumex.