Thanks, hopefully a dev can chime in and confirm...I don't currently have problems importing/exporting corrective morphs and hooking them up to be driven by joints in Maya or Unreal, just need to actually have the morphs to begin with. So once Reallusion develops the morphs, exporting from CC3 would be obviously important
to be fair for what i found looking for export target morphs and corrective joints, i ended find out which while in theory you can export the corrective morphs, it have a big chance of not work in unreal.
i will take the DAZ target morph as exemple because it was him i used to google i don't know if CC3 use the same mechanic but going from DAZ, it use dual quartenion (don't ask me what it is i really don't know deep but in basic it is a way to try to improve mesh bend and distortions) while UNREAL don't support it anymore it used to support in the past but not now, currently it only support single bend, then it means which you can't get the same perfect animation in unreal as you can get in daz, because any deform which need that system or morphs not gonna work.
basically if CC3 use the same system then it can't be exported to unreal unless as i heard you can trasnform it in a blend shape to be able to fix it but remember it gonna only work for the animation you did the blend shape, is a little complicated if you really don't know how to do that things.
the good news is which you have a "mod" for unreal which for what i read is this one:https://github.com/AlienRenders/UnrealEngine/tree/4.21
(you need to log in github to be able to proper open the link)
you need to compile your unreal with it to make a moded unreal which will allow to use that system then with that you can proper export that corrective bones but you can only work with it on that "modded version".
As i told if CC3 use the same system then probably even if they allow morph target to be exported this part could not work, if is a diferent system then you need to test for yourself to see if it will work on unreal or a DEV team come and say which it works(if they tested it).