It would be helpful to see if a child item contains an additional level of items inside.
For example, some projects (cards) are too small to warrant the use of dependencies but we still like to use child items to list the tasks that a user should complete inside the project and track the progression as they get marked completed. But those tasks might contains additional sub-tasks listed as child items inside and there is currently no easy way to even know that they might exist.
Example :
Project A (Card)
→ 3D modelling (Child item)
→ Select hardware (Sub Child items)
→ Create part models
→ Create assembly
There is a couple of way I see to address this.
The first one could be to add an icon beside the child item, both in the board and card views. This would simply let the users know that more information is included inside and they can access it if needed, while the manager could see the progress at a glance.
There might also be an option to further develop the child items in the board view but I can see how this could become quite busy visually.. (see mockup attached !)
The second might be to allow multiple "lists" of child items so that all the information can be found on one single card. Each list would have it's own title and group of child items. The board view would then probably look similar to the previous example with all task and sub-task expanded under the card.