This came up in the Note Duration thread - I'm putting it in an own thread because I am doing a MIDI specific project right now.
 
If you want to set many MIDI notes to, say, the same velocity, in X3 I would just select all those notes,
Click on "Vel" in the Events Inspector and the value would become editable - an Edit box with + and - buttons.
 
Now, in SPlat Lexington, if I open the Event Inspector and click on any of those fields, nothing happens.
Is there a setting for this?

This is crazy.
"Loop", "Punch In/Out", "Selection" - all are editable if you click on them.
But "Event Inspector" - ...nope.

It works here but it needs to be open before a selection. I had it minimized as a compact module and nothing would show up. After opening it fully it worked. 

@John - you are using Lexington, are you?
 
Just started a fresh project and a different interface (just in case).
I add a few MIDI notes to a PRV, select one, open the Event Inspector
as "Large" and after some forwards and backwards, I finally get the
Event Inspector to display the value of a selected note. (Does not want
to display anything at the first attempt)
But if I click on a value, I cannot edit anything, not in "Large", "Small" nor popup.
 
On the other hand, if I collapse "Select", "Loop" and "Punch", then hover over
any of them so that the window pops up, I can edit any value in this state, too.

I'm using Lexington.  I'll look into this more deeply. In the meantime I would send a problem report to CW. It does work but not as it should. Your last post is not that different from what I found. 

I have just stumbled upon the following.
 
If I open the separate PRV view, add some notes and click on them, then click on a value in the Event Inspector, then:
 
in X3e, the clicked-on value in the Event Inspector becomes editable,
in Sonar Platinum Lexington, it does NOT become editable.
 
But if I click on a note in the PRV view in the TRACK - THEN I can edit in the Event Inspector, both in X3e and in Sonar Platinum Lexington.

I think I am losing my mind.
The more I try reproduce the issue, the more stable it becomes.
 
I am now at the point where if I start a fresh project and add some MIDI notes, the Event Inspector will display and allow editing in ALL of its guises: Mouse-Hover-Popup, Permanent-Small or Permanent-Large.
 
Not only that, it is working regardless of whether I click on a note in the PRV view window or in the Track itself.
And yet when I started chasing this bug, the Event Inspector would at first not even display any values at all when I clicked on a MIDI note in the PRV view window. After some time, I was able to click in the Event Inspector (still blank, it displayed no values at all) yet when I clicked on a field, it opened the Edit box with the +/- spin buttons, and not only could I edit, but the value it contained was that of the selected MIDI note! - and the other fields were still blank!
 
It is as if there are some variables that were uninitialized when Platinum got installed, then as you mess around, these get set (and, perversely, saved when you close Sonar) until, as seems to now be the case, it works as expected every time.
 
@John: I will file a bug report.
Thank goodness you had similar effects, I was beginning to doubt my sanity.

No, I got happy too soon.
Now I started a fresh project, BLANK (no template at all), with nothing in my project at all I opened the Event Inspector and it already contained values.
 
I added one single MIDI track, opened the PRV view (Alt+3), added one note, clicked on the note in the PRV and the values in the Event Inspector stayed the same (not those of the note I added) and not only that, the values were once again not editable.
 
I closed Sonar totally, restarted, new BLANK project, first checked the Event Inspector and it was blank.
Added a MIDI track, opened PRV view, added  a note (C3 - so I can remember),  I selected the note and the Event Inspector stayed blank. I clicked on Note and the edit box opened with C3 as its value.
 
I have been playing around some more, writing down my steps but getting total random, non-reproducible behavior. Not sure how I am going to formulate a bug report within the constraints of the Reporter, but I'll try.

Just tried to reproduce this for you Jpetersen unfortunately I was not able to reproduce.  Here is the recipe I used.
 
1. Start SONAR Lexington
2. Click new project from start Screen. (i.e. use default template)
3. Insert dim Pro select EP patch
4. Add three bars of notes, all 1/4 notes of velocity 100.
5. Select a single note by lasso method.
6. In event inspector click on event velocity, type a new value of 85.
7. Open Event list and check note velocity has changed. Note had changed to new velocity of 85 as set in Event inspector.
 
I repeated step 6 to change the Velocity to 110 using the +/- gadgets I also changed note lengths in the same manner. 

@Wookiee - Thanks very much.
 
If you have the time, try with clean projects (New - Blank Project -) and open the Event Inspector in "Large" mode to keep it open - altho', as John already noted in his very first reply, the E.I. behaved differently in Hover-Popup and in Large mode when he tried it. - and then add just one MIDI track, open the PRV view to add a note and then mess around. If it seems stable (sometimes the note and the displayed value are not the same - that caught me once) then close Sonar and try again.
 
Tedious stuff. Only if you have the time.