Relation between level, animation, morph target player and UMG/UI


As experimentation I try to simulate a basic character creator.

At start my level is empty and display the UI.
If I click on the button, I wish to display and character and link his morph target to the UI slider.

But I meet two problems :
Impossible to add a new player to the empty level
If there is a default character, impossible to link the morph target and the slider.

However, from tutorials here and there, there’s not doubt it can be done with BP. As far as I can see, my approach seems to be confused by the relation and hierarchy between BP.

Does anyone could provide some tips and tricks? Currently my guess my problem is related to variables and there scope but… now I’m drying up.