Thank you internet.
1. yahoo search (yeah I'm old school)
2. "how to force Flash objects to a certain volume when they appear in the volume mixer"
3. results from yahoo
4. first result: http://blog.nirsoft.net/2011/02/25/how-to-control-the-volume-level-of-specific-application-from-command-line-on-windows-72008vista/
5. Winner winner chicken dinner! Hope it works on Win10
How to control the volume level of specific application from command-line, on Windows 7/2008/Vista