I am confused about the Smart tool when comping.
 
First of all, it won't slip edit (crop or fade) the ends of adjacent unmuted clips. It never shows the square icon for cropping or the triangle icon for fading in or out.
 
Second, there are three things that it does while moving the cross fade icon.
1)
Most of the time it just moves the start and end portion of adjacent unmmuted clips.
2)
Sometimes it crops one of the adjacent unmuted clips.
3)
Least of all, it actually cross fades.
 
Am I doing something wrong or do I have a setting wrong somewhere?
 
I hope I have described this well.

Thanks
Tom
 

From time to time smart tool is not doing what I want either.
 
I just go to the individual tools in pallette instead. More operations, but you get the job done - and can have nightmares later on the subject.
 
To make that easier, I put all the tools beside smart tool, on F5, F6, F7, F8, F9 so I can quickly rotate to whatever tools I needed in each spot. There are 2,3,4 on each for some.

I think it's by design that you can't independently slip-edit or fade boundaries at splits created by the Comping tool because this would break comping functionality. If you need to be able to do that, you can heal the comping split, and create a conventional split. But mixing comping and conventional splits may cause confusion later as auto-muting/unmuting of comped clips across lanes won't be consistent.
 
Your issue with the cross-fade tool may have something to do with that. I haven't really seen a problem with it, but I don't use it extensively.

I think this was happening to me as well, but I didn't realize it.  I was just reading that in Take Lanes when a clip is split due to recording in the Comping mode, a Crossfade is created.  I think I have that right, anyway.  I don't know if that's new to Platinum or not, I just hadn't encountered it before.
 
I split several clips that were in their own Take Lanes yesterday and then deleted the fragment clips, if you will.  I think I was then left with half of the Crossfades on the remaining clips, but I didn't know where they had come from.  Probably better to crop or slip edit.

olemon
I think this was happening to me as well, but I didn't realize it.  I was just reading that in Take Lanes when a clip is split due to recording in the Comping mode, a Crossfade is created.  I think I have that right, anyway.  I don't know if that's new to Platinum or not, I just hadn't encountered it before.

 
I thought that was what Auto Crossfade was for.  I tried it and it didn't work.  There still aren't any crossfades for me. This is disappointing.

I agree with brundlefly that the first behavior you mentioned is by design. My technique to achieve what you want is to lock the position and data of all the adjacent clips (in all lanes) by selecting them and hitting Ctrl+K, then drag the edge of the clip you want to slip-edit or fade to left/right (if you don't want the clips in the other lanes to move too, just lock them too).
 
As for #1-3, #1 is the normal behavior if you mean moving the cross fade icon to left/right. #2 should only happen after you made some edit to the split clips. #3 should only happen when you drag the split point up/down.

Here is documentation regarding Crossfades and Comping that helped me.
 
https://www.cakewalk.com/Documentation?product=SONAR%20X3&language=3&help=Arranging.46.html
 
Yesterday was the first time I ever used a Crossfade.  I didn't know how to use one, but the literature and videos I watched all mentioned that clips had to overlap.  A few times I tried to split a clip and then slide one of the splits to overlap the other...that made absolutely no sense to me to begin with, but it didn't work anyway.  Then I found the info above and saw that as soon as I split a clip in a Take Lane, the cursor changed to the Crossfade tool.  I just had to drag Up-Down or L-R to actually 'see' the fades and manipulate them.