There is an issue with your Y_List:

besides that, you will run into issues with the "List".
As an alternative to Add Variable (), you can start with a variable_expr, add more variables, and then use it in the Graph Builder command.
Independent of the approach, the correct positioning of Eval , Eval Expr, Expr, and NameExpr in the code is essential.
the details can be found in the documentation
... and in some community posts
https://www.google.com/search?q=expression+handling++site%3Acommunity.jmp.com
Variables_Expr = Expr(Variables (X(:age)));
For( i = 1, i <= N Items( Chosen_Ys_list ), i++,
Insert Into( Variables_Expr, Eval Expr( Y( Expr(Name Expr(As Column( Chosen_Ys_list[i] ) ) ) );
)));
Eval (Eval Expr(dt << Graph Builder(
Expr(Name Expr(( Variables_Expr ) ))
)));