A misplaced move or an edit that changes more than you intended can interrupt molecular modeling fast. The instinct is often to press Undo repeatedly until the structure looks right. But if you are unsure what actions came before the problem, stepping backward blindly can make it harder to understand the document’s state—and some operations cannot be undone.
SAMSON provides a History view for each document. It lists undoable actions and lets you move through previous document states. This makes it useful not only for reversing a recent change, but also for checking what happened during a sequence of edits, building steps, or structural movements.
Open the history before you start undoing
Open the view from Interface > History, or use Ctrl+3 on Windows or Linux and Cmd+3 on Mac. Because every document has its own history, first check that you are looking at the document you intend to change.
You can move through the document’s states by clicking actions in the History view. This gives you a more visible way to navigate the sequence than relying only on repeated keyboard presses. If you know the change you want to reverse, use the listed actions to orient yourself, then move back carefully and check the structure after each step.
Use Undo and Redo deliberately
Undo reverses an action; Redo reapplies an action that was undone. You can choose them from the Edit menu or use the shortcuts:
- Undo: Ctrl+Z on Windows and Linux; Cmd+Z on Mac.
- Redo: Ctrl+Y on Windows and Linux; Cmd+Y on Mac.
A practical approach is to undo one step, inspect the document, and decide whether that was the change you meant to reverse. If it was not, continue one step at a time rather than issuing a long run of shortcuts. Once the intended state is restored, pause to confirm that the structure and the surrounding context are as expected. This small check can help prevent a second round of guesswork.
Redo is useful when you have gone back one step too far or want to restore an action you just reversed. As with Undo, use it incrementally and check the result. The History view can help you understand where you are in the sequence of document states.
Know when the history may not be enough
Not every operation is undoable. The documentation warns that when non-undoable operations occur between undoable ones, SAMSON may not be able to undo the sequence properly, and this can result in data loss. So, if an attempted undo produces an unexpected result, avoid assuming that repeated undoing will safely reconstruct the earlier structure.
For uncertain or important changes, a cautious habit is to inspect the history before acting and to verify the document after each reversal. If the action sequence includes operations that cannot be undone, treat undo as a limited recovery aid rather than a guaranteed way to restore every earlier state.
Undo and Redo are most useful when paired with awareness of the action sequence: the History view helps you navigate, while deliberate, stepwise checks help you recognize when you have reached the state you wanted.
For the full explanation, see the SAMSON History: Undo and redo documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.