I have more than 10 years experience in digital advertising and more than 5 years of managing google analytics event tracking setup, goals/conversion setup, funnels and monitoring the performance of the marketing related setup such as UTM parameters, Conversion value, and attributions
Let me know what are the channels and definition that you want to create the custom channel groups for visualisation. The custom channel can be defined using any GA dimension such as Campaign / Source / Ad Content and etc. Once the custom channel groups are ready, you could view it under Conversion tab
For goal funnels, let me know too what is the goal type and the steps sequence, either it's a destination goal or an event goal. You may want to include the first step to ensure the funnel conversion rate included only the conversions that gone through the first step (eg. the Landing Page)
Do drop me a message to discuss further.