Hi ... I don't think there is a command available to "export" the hole table content.
I use my ui-table handler subflow to take care of all the tasks around ui-table.
it holds a copy of your table-data, tabel edits and table config (useful for replay on browser reconnects)
and you can export the table context too ... (merged tableEdit into tableData)
this is the latest Version:
https://flows.nodered.org/flow/35d0480ce9151b2a722fa9d185a37825
You can find it in my homie-device-table and syslog-server. (older versions)
a msg.payload.command="getTable" should give you the table array on the second output
The doc (help tab) is not 100% up to date but should do the task
