I'm working on a modification of the existing Release Burndown Chart App and need a feature that can select/deselect a few projects from the chart. When I go into the 'settings' of my app, I have the option to 'Follow global project setting' or 'choose a specific project', which will then only allow me to select either a parent project or an individual project, but not a selection of them.
To clarify: 
Is there any way for me to implement the selection of multiple projects? Ideally, just implementing the selection feature would cover the deselection, as I could just select the ones I wanted and of course the ones I wouldn't want would not be selected.
Any and all help is appreciated. Thank you so much.
There's not a way to do this in the tool, but I built something similar to this in a prior customer hackathon. Check out this app: https://github.com/RallyCommunity/MilestoneCumulativeFlow
It draws checkboxes across the top for the projects that are in scope so you can select/deselect them to update the chart.