You can get a quick overview of all child cards linked to a certain Initiative by applying the Initiative "Filter children" feature.
Right-click an Initiative to open the Context menu that provides shortcuts to a variety of options.
The Filter children option is at the top of the menu.
Select "Filter Children" and all child cards linked to the Initiative will be filtered out on the Cards Workflow lane (gif.1)
Don't forget to Reset the filter from the top right side of the screen.