I would not expect for Ä+combining () above = Ä᪻ to look right except with specialized fonts. http://demo.icu-project.org/icu-bin/nbrowser?t=%C3%84%5Cu1ABB&s=&uv=0
Even if it worked widely, I think it would be confusing. I think you are best off writing Arzt/Ärztin. Viele Grüße, markus
