Allow custom "Configure For" (Productivity/Testing/Games/etc) options

I create and delete Windows VMs that use configurations similar to (but not the same as) the Productivity and Software Testing config presets. I also create and delete Linux VMs in a couple of standard configurations. It would make my life much easier and reduce errors if I could

• create custom/tweaked confiurations to use; and
• use these configurations on non-Windows VMs.

(even if this was an "advanced/expert" config option that required dropping a file in ~/Library/Application Support/Parallels Desktop/ or something)