It seems to me that template-based import can handle this nicely: http://roadmap.cintanotes.com/topic/3186-template-based-export-and-import/
I also need similar feature . This dialog used for merge/unmerge operations, but also can be used at the point of import. This dialog can be helpful for improt/unmerge configuration files, for example.
There are predefined and user defined delimiters. There are list of Recently used delimiters.
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