It is possible to edit opening properties directly in v.1.9.2 beta and later.

It is not possible to define different window types on a single surfaces in earlier versions because data for openings cannot be set directly - openings inherit from their parent surface. But there are workarounds. If you need to define 2 windows types side-by-side on the same surface, you can get round the limitation by drawing a very small hanging partition to split the surface into 2. Then it is possible to set different glazing types for each surface.

Also for upper/lower split in glazing configuration, we have seen models sent in by DB users where they have defined what would normally be a single block as 2 blocks one on top of the other, connected by a large hole in the floor of the upper block and 'merged zones connected by holes'.