In order to maintain a limited history of modifications performed over the model pgModeler implements the operations history widget (at left 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 undone or redone as well clear all the history in order start over. The storage capacity of the history can be customized but bear in mind that the bigger the amount 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 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 on Chapter 6: Advanced tools.