Hey together,
According to this post Link, Conversion Exits no longer work with RAP under S/4HANA.
Meanwhile there are a lot of alternative attributes but I haven't found one for the attribute ps_posid yet. The attribute is use for the extern view of the WBSElement:

In the CDS View a cast to a char24 is no problem, but then I get a view without dots:

So I need a view with dots.
Maybe someone here has a solution for this or even the appropriate attribute ready, which I just overlooked.
regards