You can get data from the Multi Channel Funnel (MCF) api segmented by the MCF Channel Grouping using the dimension mcf:basicChannelGrouping.
Is there any way to get attribution data segmented by a Custom Channel Grouping that a user has defined in their GA account?
If this is not possible in the MCF API, is it possible in any other Google Analytics API?
Based on several searches, it seems Custom Channel Groupings are indeed NOT available in the MCF API, as of march 2017.