In order to maintain a limited history of modifications performed over the model, pgModeler implements the operations history widget (at the left portion in the image below). Through this widget, the user can visualize the details of each operation executed over one or more objects, control which operation must be undone or redone as well as clear all the history in order to start over. The storage capacity of the history can be customized but bear in mind that the bigger the number of supported entries the bigger will be the consumed memory which can affect negatively the overall tool's performance.
Another useful tool is the model objects widget (at the right of the image) which permits the user to see, in a hierarchical or listing way, all the database model objects. Additionally, it's possible to do modifications to any of that objects by selecting them and activating a context menu. A complete description and usage of this tool can be seen in Chapter 6: Advanced tools.