To export expenses you need to:
Go to the Import/Export menu. Here, you can choose the Format, Date Range, Expense Type, Tag Type and Tag Value for the expenses. Once you've selected these, you will see the summary of the export under the Summary field.
You can select the Include Previously Exported option if you'd like to include the expenses that have previously been exported.
Click Export.
If you're happy with the exported expenses, click OK to mark the expenses as exported. This flag relates only to the export template being used and the expenses will still be available for other templates.