@konradh,
I was able to get the "Do nothing..." function to work for all bindings except those marked as reserved. I did this by going to Edit / Preferences, selecting the key I want, finding "Do Nothing: used to block pre-defined accelerators" in the function list, and then hitting "Bind" and "apply." I totally agree that it's a huge miss that one cannot more easily toggle all function keys on or off. I still cannot get the keyboard pass-thru to work for plugins like Melodyne, meaning I can't start/stop playback with spacebar if the plugin window is maximized (which it needs to be in order to see properly.) I've been using Cakewalk products for almost 20 years now, I keep a very clean system, and I'm STILL spending a big part of each day futzing with crashes and weird app behavior. I wish they would just fix stuff.