From an earlier post on the Adobe Forums
Lightroom's support for a second display has definitely helped my workflow. I hope the team will consider adding more flexible multiple monitor support in version 45. Here's why.
I've recently experimented with running one of my three screens in portrait mode. When this screen hosts Lightroom's secondary display window in Loupe view, my verticals finally get equal real estate for editing. While I've not done hard statistics on my library, I know more than 50% of my imagery is in portrait orientation.
I'd like to see LR5 support multiple screens so I could set up as follow:
Screen 1 - main lightroom interface, would not need to be calibrated, for controls and navigation
Screen 2 - Portrait orientation, loupe view - this would be a calibrated display, all develop changes to verticals would be judged on this screen
Screen 3 - Landscape orientation, loupe view - another calibrated display, all develop changes to horizontals would be judged on this screen
If Adobe could make the app intelligent enough to route the image to the correct screen based on orientation (recognizing and respecting cropping that could change orientation) my edit sessions would certainly speed up and I could maximize the productivity of multiple screens.
I'd be happy with this, but I'm also stymied by the need to switch back to Library mode to tag images when my primary workflow has me in develop. Ultimately everything depends on the quality of the image. Before I invest in image-specific meta data, I have to process or at least "test-process" an image. IMO the Quick Develop panel is useless, once you become accustomed to the granular control of the develop sliders, it just doesn't cut it.
In the three monitor setup I described above I'd love to be able to configure screen 1, with a combination of panels from Library and Develop, so I could stay "develop centric" with immediate access to keywording and meta. The two additional screens would intelligently handle image display.
I think this might speed my workflow by 33% and having just returned from a Tour de France project that generated 23,000 images I need all the productivity help I can get.