/usr/share/gnucash/ui/gnc-plugin-csv-export-ui.xml is in gnucash-common 1:2.6.1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | <ui>
<menubar>
<menu name="File" action="FileAction">
<menu name="FileExport" action="FileExportAction">
<placeholder name="FileExportPlaceholder">
<menuitem name="FileCsvExportTree" action="CsvExportTreeAction"/>
<menuitem name="FileCsvExportTrans" action="CsvExportTransAction"/>
</placeholder>
</menu>
</menu>
</menubar>
</ui>
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