Do you have an example workbook at all that you could attach?
I imagine you are wanting to use a dual axis to have multiple marks available. You can do this by duplicating your Measure Values on your Rows and right clicking and select dual axis/synchronize axis. You will then have multiple options in your Marks area where you can select the first one to be circles, and the second one to be a moving average with a line.
Yes Andrew that's what I am doing. In your example there is only one measure but in my case I have multiple measures so, I am bringing "Measure Values" two times on the row shelf just like you brought "Avg(percent) but for the second "Measure Values" I double click on it and then deselect the measures that I have in my first "Measure Values" (which are percentages) and select the moving averages for my second Measure Values and then when I click OK I can see six measures but all are moving averages.