Wow, I just solved this!
Make sure you aren’t doing full screen output via the preferences panel.
Set up a workspace layout that just has your program monitor maximized on your second monitor.
You can toggle full screen with this layout by pressing control+` (that’s the tilde ~ key with no shift)
Make sure full screen is toggled off when you’re doing color correction. (still have maximized program monitor so almost just as good)
Open up looksbuilder from a clip you’re editing and go to Magic Bullet Looks -> Preferences.
Under External Video, choose the monitor you use for color.
Under Mode, choose the one that says full screen at the end of the
name.
At the very bottom, check Update While.
Exit preferences and click on Magic Bullet Looks -> Use External Video
Now when you open looksbuilder, it can stay on your not-color correcting screen like it usually does, but your color monitor will update with whatever you’re doing in looksbuilder now.
BLAM! If anyone has trouble following what I said here, I can make a screen recording of how to do it if needed. Just let me know if you need.