Have been trying to figure out why the proliferation of controllers in PRV controller panel ... as I've complained before, you have to close one line per controller per track PER CHANNEL.
Finally tracked down one source of the proliferation: Bounce to Clips ignores channel setting in the midi data and changes all controllers affected to be set to the midi output channel of the track. They are different things, so this is not good.
While for many purposes the channel number in a midi stream is ignored, it can be useful (each event, note, controller, pitch bend, etc, has a channel number field). The 'channel', same name, different thing, that carries a stream of data to an instrument, VST or otherwise, applies to everything in the track, regardless of the channel number on each midi event.
This is a design flaw, or bug.
Procedure: Load a vst instrument that can accept multiple midi streams (channels). I use Kontakt 5. Set up two midi tracks, output to the VSTi, midi channel 1 and 2, Load two patches into the VSTi, one on the first channel, a different one on the second channel.
Open PRV, create a note in the first track. That makes a "midi clip" containing one note. By default, the note event will be midi channel 1. Close PRV
Open PRV for the other track, create a note. That makes a midi clip containing one note. By default the note event will also be midi channel 1. (This is midi channel 2, but whatever ... the event channel does not matter for most purposes).
Add a controller. Midi event channel 1.
Select all midi data, Now use 'bounce to clips' -- suddenly all the midi events on track 2 are set to channel 2.
That's untroubling when you are working with 2 tracks, but how about 40-50 tracks, running to multiple VSTs? Each will necessarily use a track-based midi channel, but the EVENTS on the track need not and should not have that number as their channel number. Do a little copying, pasting, and the channel numbers proliferate. Bounce to clips occasionally, then keep working: the channel numbers keep proliferating.
And THEN you get the wild mess that drives crazy anyone trying to use the PRV controller pane --- one line per controller PER MIDI CHANNEL IN THE EVENT per track. For a medium sized project, the controller pane is simply unusable, it is a mess of lines, too small to even close them one by one by one by one by one by one by one by one by one by one.