A misplaced atom, an unexpected transformation, or an edit that changes more than intended can interrupt a molecular modeling session. Undo is a natural first response—but in SAMSON, not every operation is undoable. If an undoable action sits beside operations that cannot be reversed, undoing may not work as expected and can even result in data loss.
A safer approach is to treat the document history as a way to inspect and navigate document states, not just as a button to press repeatedly. That small change in habit can help you recover from ordinary editing mistakes while reducing the risk of undoing past a point you meant to keep.
Know which document’s history you’re using
Each SAMSON document has its own history: a list of undoable actions performed on that document. Before you navigate backward or forward, check that you are working with the document whose changes you want to review. This is especially useful when you have more than one document open or are switching between building and moving structures.
Open the History view from Interface > History, or use Ctrl+3 on Windows and Linux, and Cmd+3 on Mac. In the view, you can click actions to move through the document’s previous states. You can also navigate from the Edit menu using Undo and Redo.
Use history to find the change—not just to rewind
When something looks wrong, first identify the point at which the document changed in an unwanted way. The History view lets you move through states by selecting actions, which can be more deliberate than repeatedly triggering Undo and trying to remember how many steps you have taken.
For example, if a structure no longer looks as expected after a series of edits or movements, step through the available history and observe the document as you go. When you reach a state that helps you understand what happened, pause before making further changes. This turns history into a troubleshooting aid: it can help you locate the point where the result diverged from your intention.
Shortcuts for quick recovery
For a straightforward, recent change, the keyboard shortcuts are convenient:
- Undo: Ctrl+Z on Windows and Linux; Cmd+Z on Mac.
- Redo: Ctrl+Y on Windows and Linux; Cmd+Y on Mac.
Undo moves back through document states; Redo moves forward again. If you are unsure what the next shortcut will reverse or restore, open the History view and navigate there instead. The view is particularly useful when you want to understand a sequence of edits rather than reverse only the most recent action.
Take extra care around operations that cannot be undone
SAMSON’s documentation notes that not all operations are undoable. If non-undoable operations occurred between undoable ones, SAMSON may not be able to properly undo the changes, and data loss may result. So, if you encounter unexpected behavior, avoid assuming that repeated Undo presses will safely restore every earlier state.
A practical habit is to pause when an undo does not produce the result you expected. Use the History view to inspect the available actions and states, and be cautious about continuing to undo across a sequence that includes operations you cannot reverse. For important work, consider keeping a separate saved copy before making a sequence of changes you may need to revisit; this is a general precaution, not a replacement for understanding which operations are undoable.
In short: use shortcuts for a clear, immediate correction; use History when you need context; and slow down when non-undoable operations may be involved. These habits are useful while building molecules, editing structures, or testing transformations.
Read the SAMSON documentation on History: Undo and redo to learn more.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.