HI, martinadusk ,
Thanks for your post and for using our plugins.
If you're talking about filtering products by category, please, read this: https://stockmanagementlabs.crunch.help/atum-export-import-pro/exporting-from-scratch#filtering
On the other hand, if you want to sum stocks grouped by category, this isn't possible with ATUM Export. You must use a Spreadsheet software after exporting the data, sorry.
Purchase Price is a product's field. It isn't stored in the Order items fields, so it isn't included in the Order entity. If you need to include the purchase price when exporting sales data, you'd need custom development.
Unfortunately, we don't provide this service, so you'd need to hire a freelance developer to help you.