Better alternatives to a nested list view

I was given a task to redesign a digital time card tool for the construction industry.

What I am looking to do is to perhaps find a better alternative to a nested list view. The idea behind this view is to be able to add and manipulate cost codes (a specific type of work being done on a construction project)

Here is a screen shot of the nested list view of cost codes:

Here is a screen shot of the view when a user goes to select a cost code to enter the list: