Yes, you can update existing use cases using the "Import" functionality in Accompa.

To achieve this, include a column for Use Case ID in the CSV file being imported, and make sure that the values in this column have the proper format of UC-N, where "N" is an integer corresponding to the Use Case ID of an existing use case.

In Step-3 of Import Wizard, match this column with "Use Case ID" from the 'Accompa Fields' picklist. When you click the 'Import' button - the existing use cases will be overwritten with values from the CSV file.