To try out the solution suggested in this article you need to:
have access to the Model Comparison Tool or ROI Analysis Conversions reports
export advertising data to Google Analytics with Funnel's Google Analytics Upload product
When using Funnel's Google Analytics Upload, your advertising data is being exported to a Google Analytics Data Set and mapped to utm_source, utm_medium and utm_campaign values. If you have a Custom Channel Grouping set up in the same Google Analytics View that this data is then used in, you may be able to use that for comparing your ROI across Channels, for example.
What is important to determine or adjust before trying to do so, is if that Custom Channel Grouping is built based on utm parameters only - remember that the advertising data that Funnel exports to Google Analytics is only mapped to utm parameter values!
If this checks out, then you should now navigate to:
Conversions > Attribution > Model Comparison Tool or
Conversions > Attribution > ROI Analysis (Beta).
Here, you will be able to view Spend, Clicks, Impressions and ROAS while using either your MCF or Default Channel Grouping as a primary dimension!
If you have unsuccessfully tried to customise the Cost Analysis report in a similar way, here's a likely reason why.