A misplaced drag, an unintended edit, or a transformation that does not look right can interrupt a molecular modeling session. The first instinct may be to repeat steps until the structure looks familiar again—but that can make it harder to track what changed. SAMSON’s History view offers a more deliberate way to move through a document’s previous states and use undo or redo while working.
Start by opening the history for the document you are editing. In SAMSON, choose Interface > History, or use Ctrl+3 on Windows or Linux and Cmd+3 on Mac. Each document has its own history, so make sure you are looking at the document whose edits you want to review.
The History view is useful for more than reversing the latest action. It lets you move through document states by clicking actions in the history. That gives you a way to inspect how a structure reached its current state, rather than relying on memory—especially after a sequence of edits, building steps, or object movements.
Undo one step at a time—or review the sequence
For a quick correction, use Undo from the Edit menu or the keyboard shortcut Ctrl+Z on Windows or Linux, or Cmd+Z on Mac. If you undo too far, use Redo: Ctrl+Y on Windows or Linux, or Cmd+Y on Mac. The same Undo and Redo commands are available from the Edit menu.
When you are unsure which step caused an unexpected result, use the History view to navigate through the recorded states. For example, after trying a series of movements, you can revisit earlier points in the sequence and identify where the structure stopped matching your intention. During molecule building or editing, the same approach can help you review prior stages instead of trying to reconstruct them by hand.
Know the limit before relying on undo
History is helpful, but it is not a guarantee that every operation can be reversed. SAMSON’s documentation notes that not all operations are undoable. If non-undoable operations occur between undoable ones, SAMSON may not be able to undo the sequence properly, and data loss may result.
That warning is worth keeping in mind when experimenting with a complex document. If an action cannot be undone, repeatedly pressing Undo may not restore the document as expected. When the result matters, pause if the history behaves unexpectedly rather than assuming every step can be safely reversed. Use the History view to understand the available sequence, and treat undo and redo as tools for supported operations—not as a substitute for checking what an operation does.
A small habit that saves time
When a modeling change surprises you, take a moment to inspect the history before making more edits. Confirm that you are in the right document, move through the recorded actions, and use Undo or Redo deliberately. This simple habit can make it easier to recover from ordinary editing mistakes and to understand how a structure arrived at its current state.
For the full explanation of the History view and its controls, read the SAMSON History documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.