as i told here:
https://www.reallusion.com/FeedBackTracker/Issue/exporting-skin-details-layers
a option to be able to export each detail layer in a diferent texture instead of all aways being loaded direct into the skin, we be able to export the alphas or transparence for the details like, lips, scars, eyebrows, make up, eyes cheek marks, tattoos wounds and things like that.

when exporting your character to engines like unreal you can enable that option the it will allow you to have that "extra detail" in another file instead of the main skin texture file, then with that you can go to unreal and load that detail as a mask to be added external in game in the unreal, like most peoples do when creating complex character customization systems.

Normally you get the "base skin" with all its maps, and any extra detail will be on its own map to be added in game.

take the demo video for the make up as exemple
https://www.youtube.com/watch?time_continue=44&v=IYPCHltLWko
then after you finish the customization in the video when you choose to export the character then you can mark a option where each detail will be exported on its own map instead of exported direct in the skin them you can use that transparence/alpha to configured to be applied manually in game in a character customization where the player will be able to choose that option.

Anyone which liked that idea please vote for it!!!!!.