Final Cut iPad: How to change from Stereo to Mono?

Hey,

i`ve recorded a multiclip with one external mic (attached to the iphone). The Audio is Stereo for this clip, but the mic is only on the right side. So i want to change it to mono, but i cant find a option to do that.

The help article referes to something that does not exists (if i click inspect, speaker symbol, 3 dots, i can only copy, paste or undo events, not change audio settings as they write).

So how can i change from stereo to mono? Any one knows?