There is a simple approach to accomplish this in a few steps:
1. Copy (don't move) the QVW file to the new folder or under its new desired name.
2. Go to the original document's tasks under Source Documents, and copy the task
3. Go to the new document, and click on the Paste Task button
4. Rename the task, if needed, to a more appropriate name
5. Remove the task from the original document
6. Delete the original document
If you skip step 5, no worries, the tasks the document had will be found under <Orphans>