Removal of Duplicates (from Import)

There ought to be a way to tell the importing tool not to import duplicates.

I have a working spreadsheet of my comics. If I add new issues and import that same spreadsheet, I will end up with many duplicates. Additionally, there should be a way to click text search any items not found. By clicking this it will run a search in a new tab/window and if matched, remove it from the list of unfound items. Keeping this list of unfound imports tied to the account could come in handy.