A multimedia editing system for editing a scenario that defines the details of a multimedia application. The system presents to a user only media materials permitted to situations at a current time in the scenario under editing (a current scenario time) to facilitate a selection of media material. The media materials are divided into a plurality of types. Each of the types may have at least one format, a part of which is supported by the system (supported formats). Each media material is associated with a type, a format and an availability code of the material in a material table. The availability code indicates one of predetermined states of each material. In response to a change in one of situations that affects an availability of materials of a certain type and/or a certain format, the availability code of a material affected by the change is updated such that the availability code of each material reflects a current state of the material. Media materials of the supported formats are displayed in different ways associated with said predetermined states according to said current state of said materials.