I use 5 displays regularly for video editing and would love to use more than 2 for Lightroom.
BTS - CRG9 in PBP mode (main screens), LG UL 950-w (reference monitor), iPad via SideCar (reference monitor), + MacBook screen (scopes).
I'd love the option for 2 Loupe Displays like in Premiere with multiple Playback outs - one on the LG and one on the iPad for cross referencing color (most people will view final images on their phone so the iPad is a good spare viewer to use).
Also if it were possible to have a 3rd secondary display locked on Grid view that'd be useful as well instead of toggling tabs.
There are separate posts as per a request for waveform, vectorscope, etc so I won't go into depth on here, thanks!