Does the Premiere Pro Panel SDK allow to create a custom keyboard shortcut for a functionality? If not, is the Plugin SDK let you do that?
If you are scripting your own functionality, to be accessed via your panel, then you could add a keypress event listener to your script such that a certain function would trigger on a certain keypress ... but only if your panel was active at the time. Is that what you're looking to do? Or are you just trying to add a keyboard shortcut for a function that already exists but is currently not mappable through the Premiere's Keyboard Shortcuts window?