In order to delete one of your import tasks, just click on the trash can icon on the right-hand side.
Deleting your task doesn't equal with deleting those products from your Shopify store. Syncee never deletes already uploaded or updated products from your store. If you would like to erase them from the store, please go to your Shopify account and manage it there.
What if you want to update these products later, but you previously deleted the import task?
Syncee forgets the field mapping settings of those products where the import task has been deleted. In order to update these products again, you will need to reset the same field mapping settings for these products so as Syncee finds them in your Shopify store.