I want to export adresses in one category, not all. How to do it?
One way is to sort your contacts by category. Then you click on the group header (your category) or select all the contacts you want from the list and choose Save As. This will save (export) all the contacts to a single vcf file.
The export option from the menu (Menu > File > Export > Export contacts to vcf file) gives an additional option to export to individual vcf files for each contact, but that will only allow you to export a complete folder, not individual categories. To over come that, you could temporarily copy all the contacts in a category to a separate folder and then export from the menu.