* in the undo/redo list use an object's label and not the internal name
* check by the transaction ID instead of name to open a transaction to make the workbenches independent of implementation details of the core system
* when rejecting a task do not call undo() because this is not the same as aborting a pending transaction
* this also fixes the warning: <App> Document.cpp(1182): Cannot commit transaction while transacting
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