Undo from the actions box. The system will present
a list of the transactions which you have permission to undo.
.. Transactions which involve changing content remain undoable until one or more objects modified by the transaction are modified by a subsequent transaction. Normally, this means that only the latest transaction to an object is undoable, unless the later transactions are also undone.
It is also possible to have transactions above the transaction in the list which do not effect the ability to undo a change a user wishes to undo.