A small edit can have a big effect in a molecular model. You move a structure, build or change part of it, and then realize the result is not what you intended. The immediate instinct is to press Undo—but in a complex session, it helps to know what SAMSON considers reversible and how to see the document’s recent states.
Every SAMSON document has its own history: a list of undoable actions performed on that document. The History view lets you inspect that sequence and move through earlier document states. This is useful not only for correcting a mistake, but also for understanding how a structure reached its current state.
Open the History view
Choose Interface > History, or use Ctrl+3 on Windows and Linux and Cmd+3 on Mac. From the History view, click an action to move through the document’s recorded states. You can also use the commands in the Edit menu.
Undo and redo, with context
Undo steps back through undoable actions; Redo moves forward again. The keyboard shortcuts are Ctrl+Z and Ctrl+Y on Windows and Linux, or Cmd+Z and Cmd+Y on Mac. The same commands are available from the Edit menu.
When the change you want to reverse is recent and clearly visible in the history, Undo may be all you need. When you are unsure which action caused the unexpected result, the History view can provide context: review the sequence and select a point in the document’s history rather than repeatedly pressing a shortcut without checking where you are.
The important limitation: not every operation can be undone
History is not a guarantee that every operation in a modeling session can be reversed. SAMSON’s documentation warns that some operations are not undoable. If a non-undoable operation occurs between undoable actions, SAMSON may not be able to undo the surrounding actions properly, and this may result in data loss.
That caveat changes how to approach recovery. If the history does not behave as expected, do not assume that pressing Undo repeatedly will safely restore the model. Pause and inspect the History view. If you are about to try a sequence of uncertain edits, consider keeping a separate saved copy of your document beforehand; this is a general precaution, not a substitute for understanding which operations are undoable.
A practical recovery routine
- Open the document’s History view. Remember that each document has its own history.
- Review the actions around the change. Use the visible sequence to identify a useful earlier state.
- Move back deliberately. Click the relevant action in the History view, or use Undo when the last action is clearly the one to reverse.
- Check the result before continuing. If you moved too far back, use Redo to return forward through undoable actions.
- Use caution if an operation cannot be reversed. The history may not be able to restore the document reliably across such an operation.
Thinking of History as both a recovery tool and a way to inspect your editing path can make troubleshooting less guesswork-driven. It is especially useful when building or editing structures, or when trying transformations and wanting to compare document states.
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.