Starting with Strategy 9, object replacement was introduced to the "Find and Replace" feature. Objects that can be replaced from include: attributes, metrics, grids, filters, templates and custom groups.
The option is disabled by default, to enable it the checkbox shown below should be selected.

The "Find and Replace" tool can be found in the "Tools" menu of Strategy Developer:

To replace an object, follow these steps:
In the example below the attribute "Year" will be replaced in the report "TestforReplace" by the "Region" attribute.

WARNING:
Object dependency replacement can result in unusable object. It is highly recommended to backup the metadata before executing this action.