Until the new dashboard controls get finalized, probably the best way to handle this is to declare the dataTable as a global. When you want to add a new node, append a new row to the table with the new data and call your draw function again. Something like this, maybe?
var data = new google.visualization.dataTable();
// populate the data table
function drawTable() {
// draw the table
}
function addNode() {
// add a new node to data
drawChart();
}