Hi Chelsea.
This is a very old post and may well have been superceded by better ways of doing this in JavaScript etc..
But yes, at the time I did solve this in a solution that did not use the flexviewer but instead was a from scratch flash player project. See screen shot from our user guide. If you have specific questions I can try and answer them but in essence I just created a project with an mxml file which was where I built out the dashboard
I then added a view stack into which I inserted areas for all the different charts (which can be expanded to go full screen or 'pop back' into their container area
I then used the mx.charts class in FLash to create the types of charts I wanted, configured them as required and bound them to my data sources. For multiple lines on a line chart you just add a line series for each line you want.
As I said I'm not convinced a flash based solution for any sort of future proof solution is going to be your best way forward but that is for you/your employer to decide. You might want to consider investigating javascript/angular/some other modern browser compliant technology, but seeing as I don't know what business problem you are trying to solve I cannot advise further.
Hope this helps a bit!
cheers
Graham