The only way to determine when the last time a schema was used would be based on the last modified date or based on the most recent record inserted into the table itself. That said, unless a field was added to track the last time it was accessed via a workflow, there isn't a way to determine whether a workflow last updated the schema.
The only way to determine when the last time a schema was used would be based on the last modified date or based on the most recent record inserted into the table itself. That said, unless a field was added to track the last time it was accessed via a workflow, there isn't a way to determine whether a workflow last updated the schema.