Susan, I am not aware of a solution for CSV file import in the Web UI. I only know the Eclipse client based solution. This can also work with the mapping files required to map attributes and their values. The only way to import work items in the Web UI is based on the MS Project XML. I believe that this does not cover all attributes.

It is possible to use the API to do this, however, it would not be a trivial task to attempt that.

What is the reason behind not using the Eclipse client? Typically this would be only used at the beginning of a project. Once work items are in the tool you should work with them. Trying to perform round trip scenarios with exporting, importing, exporting is usually a very brittle and error prone approach.

I think it would be desirable to have a way of exporting and importing work item data, probably not CSV file based, because CSV is a bad format to be used with multi-line text and the like. This would be most useful for migration purposes.

I would suggest to create an enhancement request.