Let's say I have mapped a knob on my keyboard to the cutoff control of a synth's filter. I then record a performance with this knob on that synth's MIDI track, which already has the relevant MIDI notes recorded. The controller events appear in a clip on top of the MIDI notes. When I play the track back, the filter cutoff is moving along with the controller events I recorded. So far so good. 
 
The confusion starts when I then open the piano roll view to view that data in a controller lane. A lane has appeared with the data I recorded, but the edit filter in the controller lane is labelled "CC: 5-Portamento time" instead of "NRPN: CUTOFF" as I'd expect. In fact if I click on the edit filter and select "New value type," and then select "NRPN" as the value type and "CUTOFF" as the value, a lane for that parameter appears but it's blank. 
 
What's going on here? The controller events I recorded are definitely controlling the filter cutoff (because I can see and hear it), and most certainly have nothing to do with portamento time. All I want to do is to be able to map a synth control to a knob, record a performance, and edit the resulting controller events in a controller lane. Can someone explain to me what's happening and where I'm going wrong? 
 

My guess would be that the keyboard knob is actually sending CC5 so that's what SONAR records it as. You may have told the synth's Filter Cutoff to respond to the CC5 data, but that doesn't change the data type. If you want the data recorded as an NRPN, you'll have to program the keyboard to send that (if possible).

So I guess I have to assign an NRPN to a controller. But that means I have to work out the NRPN of the parameter in question. When you select it via the controller lane's edit filter, they're listed by name and not number. Does this mean I have to bring up this list and count down the list of parameters until I come to the one I want? Seems very cumbersome. 
 
I suppose the alternative is to just accept the fact that controller lanes are not going to be labeled with the NRPN parameter name in question? 

Thinking about this from a functional point of view though, we should be able to map a controller knob to a NRPN via MIDI learn and then have Sonar record a performance with that knob to the correct controller lane though, shouldn't we? Or is info about that mapping only available to the synth?

The capability for the host to know what controller is associated with what widget in the plugin GUI may already exist in either or both VST2 or 3; I don't know the VST spec that well. This information used to be buried in the back of the paper user manual that came with a hardware module, and it was up to the user to set up the controller to send the right data on the right port and channel and keep track of everything without the benefit of "friendly names".  
 
But the fact remains that SONAR is set up to record and display the data as-recorded from the controller. When you look at an event list, it shows the channel that your controller was sending on, not the output channel of the track or the channel to which the synth is set to respond. Having an option to display the destination data format and/or parameter name rather than the source format would definitely be a new feature.
 
Obviously, this mainly gets to be an issue with Non-Registered Parameter Numbers which, by definition, have no standardized function, and could be controlling anything.
 
 

Yeah it seems like Sonar could be a lot more user friendly in this respect, especially as modern music styles make extensive use of performance NRPN's. Another thing I noticed is that in the "insert series of controllers" function in the insert menu, if you select NRPN, you have to enter the number of the parameter and it doesn't list them by name like the add controller value menu does in the controller lanes. It would be nice if the "insert serie"s menu populated itself with a list of the NRPN parameter names associated with the current track - identifying them by number is cumbersome. I hope Cake addresses this whole controller area at some point - it could definitely use some love.

Not that Cakewalk can't maybe leader on this, as they have with other technologies/features in the past, but I'm curious whether any other DAWs already handle this more elegantly. Anyone know?
 
I think the dearth of other contributors to this thread might be an indication that NRPNs are not being so widely used as you imagine. That or other members are just using MIDI learn/Remote Control and not worrying about what's going on under the hood and/or not doing much editing of the recorded data. Or they're not just not here because they use another DAW that does this better.