During almost every moment of a modeling process, you will need to have something to select which elements you want to interact with in your model, and maybe you may need to change often what to show on the models, in order to succesfully work on every element on it. For this reason, there are common tools which are available from almost every Tools Set.
Fig. 1 Parts List
Together with the section of the Selection and Visibility Tools, on the same Tools Sets you will find the Parts List.
Fig. 2 Parts List