PanelChrome does inject functionality for changing the time range (see lines 250 and 302), but it looks like there isn’t anything directly injected to set other variables (what I was seeing in my investigation was that stuff being injected into the panel header). I did find this How to change a dashboard variable value from a plugin?, and I’m currently working to understand the mechanism he’s describing.
Sorry I can’t give you any official help, just offering my understanding as a fellow traveler 