I haven't encountered that problem at all.  

Actually, viewing multiple tracks in the PRV is awesome. Each track takes a different color. you click in a pane on the right to identify the one you want to work with. It enables you to see the melody while you work on the bass line or whatever.
 
I'm not booted to windows or I'd check the event view. I mainly use the event view for troubleshooting issues. I'm not in there that much.
 
In PRV check the drop down menus in the upper left.
 
G

This is really cool.... specially the pane on the right....actually, lots of nice things...
It would be nice to be able to show all midi tracks automatically....also, overlapping notes on different tracks are obscured... would be nice to ghost them or something... maybe stack them in thin colored lines with larger key views... Ie, three midi tracks of different overlapping lengths  would be stacked... or  by shuffling the pane midi track positions would restack them on top of each other...oh... I see you can click and kinda sequence the layering a bit...so long notes can be placed underneath shorter ones (not perfect by all means... multi color  thinner lines would be best for a quick scan...
 
vids would be sweeeeeeeet...I know there comin' but this is a real nice gift...
 
But big improvements; I love it!!! PRV will be way more fun to tweak with...quick toggling pain is fantastic... PRV area is my favorite improvement todate...

There is a button at the bottom of the controller lane header that can close a lane if you don't need it. 

John
There is a button at the bottom of the controller lane header that can close a lane if you don't need it. 

Sorry.  I'm not seeing it.  Here is what I see:

 
All that stuff at the bottom is controllers for the 5 tracks I have included.  They aren't spurious.  It is a velocity, volume, and legato control for each track -- 15 lanes total.  And you get all 15 even if you have hidden all but one instrument, as I have done in this case.  I am only showing Alto sax 1, but I get all the controllers.  I can't expose them, expand them, delete them, edit them, stretch them, anything.  Completely useless, it seems to me. 
 
Doesn't anybody ever test this stuff?  This seems like a perfectly normal setup to me.  In this case, I imported the MIDI from Finale, but I could have set up those three controllers (or more) myself. 
 
Please note that with even as few as three controllers for a single track, that still is almost impossible to use, even if you use PRV in single track mode.  I would need a monitor the size of a IMax screen.
 
So I give Cake a B+ for improving the ability to edit MIDI notes and an F- for not fixing the ability to edit controller settings while they were at it.  At a bare minimum, if you hide a track, then its controller lanes should also be hidden.

It looks as though because so many controller lanes are exposed, Sonar cannot display the +/- buttons for each one.
 
Try shrinking the notes pane right down to a thin sliver, see if this helps

John
 The above is from the help file.

Thank you for posting the generic help information.  Now, could I get you to look at my example that shows it is IMPOSSIBLE to do anything with that screen if there are more than a couple of controller lanes?
 
This is a fundamentally bad design that guarantees a catch-22 if a person happens to have more controller lanes than the UI designers saw fit to test.  This has always been bad.  Now it is impossible with the multiple tracks view.
 
In addition to only allocating screen space for lames associated with tracks in view, there ought to be an "auto-zoom" option that guarantees if you can click on ANYTHING in the controller lanes, SOMETHING will expand up to a minimally useful size.
 

I can easily replicate your screenshot above.
Have you tried what I suggested and drag the divider between the controller and note panes upwards?
This should reveal enough of the controllers to enable you to access their +/- buttons
 

John
 

The above is from the help file.
Below is a screen shot with a close up the lane controls. The minus sign will remove a lane.
 
 

John,
What I don't understand is, say you have 3 tracks you're working on. You only show track 1, and then hit all the minus signs on the tracks your not working on to make it less dense. What happens if I want to then hide track 1 and show track 2 to modify it. Do I then need to delete the controllers for track 1 and add controllers for track 2?
 
Walt
 

Bristol_Jonesey
Have you tried what I suggested and drag the divider between the controller and note panes upwards?
This should reveal enough of the controllers to enable you to access their +/- buttons

Yes.  It comes nowhere close to exposing those buttons in this case.There are actually a few more controllers than I was aware of.  I think there are 5 controllers per channel -- total of 25.
 
This is a fundamentally bad UI design when it depends on buttons in a collapsible section being visible.  Always has been bad.  But it gets many times worse now that PRV can support multiple instruments.  I have identified several really simple solutions that should not be difficult to implement and would eliminate the inherent catch-22 nature of this UI design.  See http://forum.cakewalk.com/In-PRV-controller-lanes-are-practically-unusable-please-fix-this-m3166007.aspx#3166007
 

Bristol_Jonesey
Go to Tracks > Pick Tracks in the PRV.
Select just ONE track.
Delete any spurious controller lanes.
Rinse & repeat.

I don't know how to say this any more plainly.  There are no spurious controllers.  They all serve a musical purpose.
 
But even if I did have some superfluous lanes, that should not put the UI into a catch-22 that makes it absolutely impossible to use.