Select all chords on the chord track, use the drop-down menu in the info line to change the "Root Key" selected chords are transposed
That's precisely the problem.. it doesn't work with a multiple
..EDIT: Strike that.. it's working now
(I'll investigate further...)..edit: Steve, were you saying that sometimes it didn't work for you either?
I was having serious problems with this and then noticed that it seems to interact with the scale being shown. I had auto-scale turned on in the inspector. When it is on if you use a chord that is not fully consistent with the current scale (for example a major minor substitution) Cubase will change the scale to whatever it thinks best to accommodate the problem chord. I noticed that if I selected chords that did not cross scale change boundaries I could change them all from the info line. But if the selected chords were in different keys none of the chords could be changed.
So I turned off the auto-scale and often, but not always this resolved the problem. I've been using the info line to modify chords in the Chord Track quite a bit recently since I'm reading a book about chord progressions and using the track to check out examples. To do this I copy a bunch of C chords on each quarter note and modify them using the info line (faster) when I can and the Chord Editor when I can't (typically because some items are available in the editor but not the info line, like setting a 9th). So I'm not transposing chords, but rather selecting 4 chords here or 2 chords there and changing the root, major/minor, 7ths etc. With auto-scale turned off 80-90% of the time the info line changes work, but sometimes they won't take. I can't see any pattern to when it won't work. For example yesterday it let me change the 4 C chords in bar 2 to F, but in bar 5 wouldn't let me change 4 C chords to F (at this point I yelled at the monitor "but you just let me change the exact same thing"
In any case it seems you can always transpose any chord individually from the info line, independent of auto-scroll being on or off. But of course that can get tedious. If you find you can't transpose all the chords at once, you might be able to do it in two or three groupings. Sometimes it seems to not like changing both 3 and 4 note chords at the same time, while other times it is fine with it.