1. A method for editing a computer-aided design model for developing electronic control units in a design environment, the design model comprises at least one model object with first data, the first data being additional data that are used only for individual development steps of the control device, the method comprising: reading all model objects of the design model in the development environment; reading an allocation list that assigns a particular globally unique key to each model object; determining whether the first data are available, if the first data are available: reading the first data from a first memory location, wherein the first data contain the globally unique key, and then the first data are assigned to the model object based on the global unique key, so that the first data are available during editing of the design model, or if the first data are not available: assigning the globally unique key to the model object so that the globally unique key is available during the editing of the design model; editing of the design model; and saving the allocation list in which the globally unique key is assigned to the model object, the step of saving comprises: if the first data are available during the editing, generating a new globally unique key, which replaces the previous globally unique key; if the first data are not available during editing, retaining the globally unique key; saving the first data together with the globally unique key; and saving all model objects of the design model.