Edited below. Solved.

So there is one other topic like this but was some time ago (Last Year) and no resolution there. This USED TO work prior to 7.4 Update. So going to post pics and information for Reallusion to get this fixed. I am not going to make a Feedback Tracker on this as I really don't care at this point whether this works or not. All I can say is....either fix your docs/videos....or fix your software.....or both.

Note: We are using iClone7 and 3DExchange7 now as a re-targeting tool to get all animations (from our own and contract animators) on a single skeleton (1 for Female and 1 for Male). We now sub Maya 2018 and do all of our animation modifications in it in lieu of iClone7.4. Meaning we are almost done migrating away from iClone.
Don/Olander

So here are the informational pics.
76% of original size (was 665x19) - Click to enlarge

76% of original size (was 665x19) - Click to enlarge

Edit Motion Layer works perfectly fine as well as adding keys in the Motion Layers to modify animation. The Curve Editor acts like it is completely dead but the bones do show up....so it is 'not quite' dead. :)
76% of original size (was 665x19) - Click to enlarge

The following 'used to' mean that the animation data has already been established as Curve Editor Ready Data. If not....the convert option is available to convert it. Now it is always greyed out.
76% of original size (was 665x19) - Click to enlarge

So the curve editor has basically been unusable for the past 5 months and Reallusion has done nothing to fix it? I really don't understand how things like this happen. I was just about to buy the curve editor (and several other plugins during the 15% off sale) and I never would've known that it doesn't work if I hadn't stumbled across this thread. Thanks for that!

@OlanderDA

I do not see any problems with Curve Editor at the screenshots.

"Convert to Curve Data" is not applicable for iClone 7 motions or motions/clips applied in iClone 7 (post curve editor). It used to supply older linear clips with curved data.
That is if you open older iClone 6 project for instance and wish to use a Curve Editor, you'd need to execute "Convert to Curve Data" first.

Otherwise, regarding first screenshot, you just need to sample a clip.

I wondered about that after posting my reply (I haven't actually used the curve editor before, but it makes sense that you'd have to sample the clip before editing keys). I guess I'll be giving Reallusion more of my money after all ;)

@4u2ges

Tried what you suggested and it worked. Used to have to 'sometimes' go find Edit Motion Layers (or whatever the menu option was)...this option is now gone.
What is strange is that the colored Curve Editor had always been live ('sampled' by default) except for some animations added (likely related to what you wrote). 7.4 and the latest Curve Editor changed that behavior it seems.

Thanks for the feedback.

@Hookflash
Curve Editor is really a must have when doing animations in iClone (or Maya, Akeytsu..etc)....especially when re targeting various animations from different sources. Also cleans up Mocap well.
iClone7's Curve Editor was used heavily earlier in our animation conversions and editing...it is a great add on.

So if anyone else gets here and is curious....
- Add/Edit your rlMotion
- Click the Motion Track/Bar to turn it green if not already
- Right Click on the Motion Bar
- Choose Sample Motion Clip > Sample All Parts
- Curve Editor will be editable