1. A method comprising: generating for output, by a computing device, a plurality of data item graphical representations, wherein the data item graphical representations represent data items; receiving, by the computing device, one or more inputs to select two or more data items from the data item graphical representations; generating, by the computing device, in response to the one or more inputs, a hierarchical association between the two or more data items, such that the hierarchical association is determined based at least in part on the one or more inputs to select two or more data items; generating for output, by the computing device, a hierarchical data graphical representation that graphically represents the two or more data items and comprises a connector graphical element that indicates a type of the hierarchical association between the two or more data items; and switching, by the computing device, in response to a user input to select the connector graphical element, the hierarchical association of the two or more data items from the indicated type of the hierarchical association to a different type of hierarchical association, wherein at least one of: wherein generating the hierarchical association between the two or more data items comprises generating the hierarchical association with an initial default type of hierarchy, and wherein switching the hierarchical association in response to the user input comprises switching the hierarchical association from the initial default type of hierarchy to a user-selected type of hierarchy; or wherein the connector graphical element indicates the type of the hierarchical association as either a level-based hierarchy or a parent-child hierarchy, and wherein switching the hierarchical association in response to the user input comprises switching the hierarchical association between the level-based hierarchy and the parent-child hierarchy.