PrF UG projects undo edits
From Protege Wiki
Protege-Frames allows multiple levels of undo and redo.
When you use Undo, your project will be restored to its previous state. In most cases, you will not see any difference. However, while Protege-Frames always creates a state that is logically identical to the initial state you were in, in some cases internal state will be represented in a slightly different way. For example, classes or instances might appear in a different order in the .pont or .pins files.
When you use certain advanced features, you may see a minor difference in the user interface. For example, if you are using the Graph Widget, some elements on the graph may appear in a slightly different location. The project has not been affected in any other way.