Hello,
I have vendors with over 40k products. When I start the import via admin area (because ssh cron task command fail on cs-cart at this time with error that file can’t be readed) and work on server i.e. restart php , the import stops which is normal but when I start the import by selecting import only new products, it will take hours and hours to get to that point where it left. Why cs-cart don’t just jump in high speed over already present products if I select so ?
Because there is no such option 
But if we select only new products, it should only check the presence of product ID, if its there it should go on until new product ID is found in import file and import from that point, why is it taking so long to get to where it left ?
First of all, each line of the CSV file has to be properly parsed into the mapped values applicable to be imported.
Then, each product code from the file has to be checked for existence in the database.
All these operations take time to perform, and unfortunately there is no such thing as a “bookmark” in the file to simply continue the import from the “bookmarked” line.