On 16 Dec 2015 12:57 am, "Juri Linkov" <juri@linkov.net> wrote:
>
> I mean a char-folding customization that allows a search
> for “ä” match “a”.  Is this already possible? 

Not yet.
I do want to expose more char folding options, but I want to wait for emacs-25 to come out first, to see if and how people will use this feature.