I’m using Note Expression with my Roli Seaboard Rise 49. In the note display, I wish to view MIDI controller #74, which is what is sent from the Y-axis of key-waves on the Seaboard. This controller data will only display in the controller lane and not on the notes. When I checked the ‘MIDI/Note Expression/Note Expression MIDI setup’, I see that all controllers are listed as “unavailable” (please see attached screenshot). I have not found a way to change this setting.
Finally, 8 long months later, I was able to fully solve this dilemma completely on my own. 
Turns out that the solution was quite simple: In the menu dialog “MIDI/CC Automation setup” the “Record Destination” for the controller in question (in this case it is CC#74, which corresponds to the Y-Axis output from my Seaboard Rise 49) needs to be set to “MIDI part” and not “Automation Track” (which I had set a long time ago for automation purposes). Just like that, the desired controllers in the “MIDI/Note Expression/Note Expression MIDI setup” menu show an activation “X” rather than “unavailable”. So now, Y-Axis gestures finally show up as individual note expression data instead of appearing only in the global controller lane.
To summarize, there was an apparent conflict between MIDI automation and Note Expression, which can be resolved with the correct settings. There is no clue about this in the owner’s manuals. And normally, I really like to thank people who helped, especially when there is much at stake. But in this case, no one did. Not here and no response to my support ticket either. 
Anyway, this can now be marked as “solved”.