Custom Cards View

For the activities of a specific subsection, you can either select thoughts via reports or manually (cmd/ctrl+click the active thought, and then it's gates to select all relations).

You can also choose Edit > Select > Select Related for defining larger subsections based on relation and not report types.

Then with the thoughts selected, go to the cards view and choose the selection mode (looks like a checkmark)

This will show you what you are looking for. I do this quite a bit and it allows me to break down a large number of children by date and works very well.