Hi Jennifer,
You can display in MS Project work item fields of type: Integer, Double, String, DateTime, TreePath, but not Html, PlainText, or History.
But you are correct that you cannot display 'Description' in MS Project, since it is a work item field of type 'PlainText'. Still for work item fields not mapped by default to MS Project fields, you may find the help topic, "Customizing Microsoft Project Field Mappings" useful.
Here are some workarounds for using MS Project:
1) add a work item field of type 'String' to the 'Task' work item type (and any other work item types you want to export to project).
2) use an existing work item field of type string to persist the info you want to display in project.
Since 'String' fields only hold 255 characters, neither of these approaches can get you the entire 'Description' field, which does not share this limitation.
You could use Excel to bulk copy the first 255 characters of the Description field into the String field you want to use.
For more info on customizing work items types, here is a link: https://blogs.msdn.com/team_foundation/archive/2005/03/22/400674.aspx.
Regarding building a Work Breakdown Structure in Excel:
3) As you probably know you can tweak the formatting in Excel to improve the appearance of the Description field. On refresh, that formatting change is lost. You could add an Excel macro to reapply the format.
4) You are also correct that Excel doesn't show the heirarchy. A workaround would be to use another column to identify the WBS grouping for each work item. This info could be persisted in Excel only, or (preferably) another otherwise unused or new work item field. For the rollups, pivot tables would be helpful.
Please let me know if any of these suggestions are helpful for you and thanks for the good questions!
Kevin McMurry - MSFT