Using Timeline Summary as Formula

As my concern, for now Monday Timeline column is great! Because it can be used on formula column.

But, I think it will be more powerful if we can use Timeline Summary (provided from subitem and connected board) in the formula column. By having that, we can calculate every timeline summary in our formula.

In my case, I want to use my Timeline Summary that come from subitems and connected boards to calculate the left days of my project task.