Import Mendeley: how to keep folder structure?

My Mendeley library is not fully synced. So I prepare to import it via .ris resolution. But when I check the RIS file, it does not contain any info about the Mendeley library folder structure (on the left pane in Mendeley). How can I restore this info? It is critical to me because all my docs are categorized by this folder structure. Thanks!

To retain your folder structure please first sync your library, then import it to Paperpile using the Wizard.

I suppose you could alternatively export your folders one-by-one to RIS and import them one at a time, but you would also then need a way to only upload the relevant PDF files with each RIS file.

Aha, my library is too large which can not be fully synced via free Mendeley acount. As I want to migrate to Paperpile, it makes no sense to upgrade to payed Mendeley plans… Too bad, maybe I should stay with Mendeley.