I'm also trying to figure out if there is a way to do it, and I don't think there is. I've started splitting my clips, slowing down the parts I want, muting any audio I want muted (you also loose the ability to do this after you convert to a SO), and THEN converting to a SO for color correction or other filters. Sure wish there was a way. SO's aren't so smart if you ask me...
Thanks for the reply and as a work around method I used the Photoshop to do all the adjustments then export the video to iMovie to finish the final cut. I also have a problem to paint or clone on a blank video layer created in Photoshop. It tells me the time is beyond the target frame time, I don't understand the message. Can you explain to me what did I do wrong? Thanks a lot!
I'm afraid I don't know, I just happened to find your question when I posted a similar one. You need someone who knows more than I do :-).