A web-based system, method and program product are provided for adding content to a content object stored (e.g., a custom compilation or prepublished work) in a data repository as a group of hierarchically related content entities. Each noncontainer content object is preferably stored as a separate entity in the data repository. Each content entity is also stored as a row in a digital library index class as a collection of attributes and references to related content entities and containers. As the user selects desired objects for inclusion in a content object, the system arranges the objects hierarchically, e.g., into volumes, chapters and sections according to the order specified by the user. The system then creates a file object (e.g., a CBO) defining the content object that contains a list or outline of the container and noncontainer entities selected, their identifiers, order and structure. This file object is stored separately in the data repository. Content is added to the content object by adding a container or noncontainer identifier to the list or outline. This is achieved through a user interface by providing a mechanism for enabling a user to select a container or noncontainery (e.g., by title) and specify a target location for the container or noncontainer (e.g., by inserting the entity title between other entity titles on the outline.