RMS level graph as an export?

You can export the RMS values from the Acoustical Parameters module, pressing the button "Save Results to File". The default is to export just the table containing the computed acoustical parameters, in a TXT file. But if you select the alternate file format: Save As Type: Energetic IR (.CSV), you will get exactly what you need for all the octave bands plus A and LIN.
Then you open the CSV file in Excel, and format the chart as you like...