In a project I faced the issue, that I have to import large amount of data into a complex structure. The data was provided in Excel, every row reflected all the levels of the corresponding structure. (The tree was flattened into rows.) To solve this problem, I wrote a user control, which was able to import data from tabular format into the content tree. The very first row of the tabular data contains information about the document types and properties to use in the following rows, and the parent-child relations.
Since the very first prototype the import interface was moved, so it has a custom section in the Umbraco tray, no user control required, the gadgets aren't on the published site anymore.
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