Hello composers and other ghosts! 
Some time ago I felt that it would be nice to see for example all Modulation events for all selected parts in Key Editor. Then I think I can work without this extra feature, but it wwould be great to have it.
But right now I somehow accidentally select three parts in three lanes of one track and surprise - I see Modulation controller events for all three parts. And I can edit each controller the same way we can edit an active or selected track note events. Here in lanes the inactive lane’s controller event are a bit grayed or “behind” the active one. By clickin on an event of inactive lane’s controller “it comes closer” and all other “goes farther”. It’s cool!
Please tell me if this feature is switchable in parameters for multiselected Key Editor view! If not, then maybe this featur is in Cubase 10? I will upgrade soon, but now I’m composing.
Why this would be great for selected track parts? Imagine you record chello and use Modulation wheel for expression, then you record violas and also move the modulation wheel for your felt expression and so on. Then you want to manage these expressions but change viola’s expression according to chelli expression - a little bit louder or quieter but with the same curve. Now this is not possible even if you draw a new curve and switch to another of selected track to view how far your new curve is from the destination.
I hope my bad English is at least for your enjoyment 
This image shows as it is in multi Lane parts selection:
And this is my vision. Maybe something is in other DAWs, but would be great to have in Cubase:
