My issue is that a) I am unable to get passthrough working properly with the DAC and more importantly b) the DAC is connected to my AVR via toslink and therefore does not support HD audio formats or multichannel PCM
So I am looking for a comfortable solution to use the DAC for music and the standard HDMI interface for everything else.
I found a workaround in the meantime though:
Audio Profiles Kodi Add-on
For anyone interested, it allows to define separate settings for Video / GUI / Music