If I recall correctly this was the same in CC2. In order for Morph Sliders to work correctly, then exported base needed to be Reset before exporting. If you used the default CC2 character it generated issues because the default CC2 character was not the reset CC2 character...At least it generated issues for me. But, in CC3, I tried to hit the Reset button to remove all morphs before exporting and still had the problem. 

"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast

Thanks Ani and Lord. Yes you are right about default character and current morphs. I always do custom characters with presets already baked and probably used current morphs (it's been a while).

But I found a fix. Apparently CC3 is more fussy to Blender Import/Export settings, than CC2 was.
Playing with settings I was getting 2 types of errors in CC3.
One was the same as Lord had (about decryption keys) and another one I already mentioned (incompatible character).

Finally I have found an optimal Blender settings. I have selected to Export Body out of CC3, customized it in Blender and seamlessly created a slider in CC3 out of the default base female.

Import (default settings, do NOT attempt to select Keep Vertex Order):

77% of original size (was 657x19) - Click to enlarge

Export (critical setting encircled):

77% of original size (was 657x19) - Click to enlarge

Thanks. I will try that!



"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast

Does this include iClone itself?

I am looking to create some different sliders, and buttons; some ideas come to mind, both for iClone and CC3; so how do I go about doing things( sliders for iClone 7), and being to save them for selling?

Thanks 4u2ges, your solution works. And you don't have to use the default base character, but just make sure that when you import it back to CC 3, select [Source Morph: Current Morph].

I'm pretty sure you need to keep the vertex order button checked both during import and export.
The same solution is suggested here :  
https://www.reallusion.com/FeedBackTracker/Issue/Failure-using-Blender-to-Alter-obj-for-Morph-Creator