Our Export Data tool recent underwent a significant update, and since then we have been receiving questions from users about whether they can export multiple sites into one CSV file. Unfortunately this option is currently unavailable - you can export data from multiple sites but the system will automatically create one CSV per site. However, there is a workaround that involves using the Graphing tool. With Graphing, you can export data from multiple sites in one CSV file.
For step-by-step instructions on exporting data from multiple sites in Graphing, see, Export graph data.