When adding widgets to your Google Data Studio (GDS) dashboard you'll be asked to select a single data source. This means that it's impossible to group data from multiple sources into a single widget. Funnel enables you to combine data from multiple sources into a single table or chart:
As apposed to having a data source for each individual platform, Funnel combines and groups the data prior to exporting to Data Studio.
This means that you can create widgets with data from multiple ad platforms:
You can also combine your ad platform data with Google Analytics data to gain a complete overview of your marketing efforts: