This feature allows users to define which network elements are included in a given scenario's simulation. Users can enable or disable parts of the network, such as a future subdivision or a main taken out of service for maintenance. When a simulation is run, only the elements in the active topology are sent to the EPANET engine, providing an efficient way to manage different network configurations. In addition to manual selection, users will also be able to define the active facility set using queries or rules (e.g., activate all pipes with an installation year before 2025), enabling dynamic and automated management of complex scenarios.