Why do track wide effects get cancelled when going into multicamera mode? It is horribly inefficient to have to apply color correction etc to each clip from the same camera. I must be missing something. I am using Vegas Pro 12 on a Windows 10 system.
Because once you enter the multicam mode your former tracks will be canceled and a new track will be build and track fx can't get copied. You need to adopt your workflow.
Apply your effects at the Media level; that way they won't disappear.
I also usually do my multicam cut before applying any effects... but I agree that the entire concept of combining tracks into one multicam track is horribly inefficient, it should just leave the tracks expanded and apply the edits to the timeline as-is.
Also do it as suggested above. I think I'd do it that way no matter what because looking at multiple cameras simultaneously in multi-cam edit is a pretty big load that would be even greater with video effects on each camera. I expand the multicam track back to the original tracks for each camera after multicam edit and then apply most effects to each camera track. Doing it this way, effects don't get applied at all to muted clip segments which would just be a waste of time and processing power anyway. I put some effects, like luts, on the media. But I find it easier to put any effects I need to animate on the tracks so I can see all the keyframes in relation to one another and get at them all easily.
Btw, if you really feel you need to do the effects before your cuts, just save each track's effects to a filter package using the FX plugin chooser and restore them after expanding the multicam track. Handy to have if I need to quickly recreate the project in an earlier version of Vegas.