Oh, I see! Initially the import/export features were only meant to let you download and
restore backups of your collection. So that's why they use our internal set IDs, rather than the abbreviations.
However, I appreciate that it may be useful to manage your collection on DeckStats but then export it to other systems.
To make this possible, I have now added a new column to the CSV export that includes the set abbreviation for each card. In addition, I also replaced the "Card #[Set=123]" format in the text export with the more common "[ABC] Card" format.
Please have a look and let me know if this works for you!
And just out of
curiosity, which other systems you are important these into?