We would like to have a column in the explorer overview which shows manual set expiration dates for all diagrams which are also searchable.
1. Open 'Setup' → 'Define notations/attributes'
2. Pick 'Business Process Diagram (BPMN 2.0) as modeling language and then 'BPMN-Diagram' as diagram element type.
3. Click 'Add' under 'Custom attributes'.
4. Create a new attribute with data type 'Date'
By following these steps you create the custom attribute, which can also be shown in explorer as a column.
KBA , BPI-SIG-CA-SEA , Search for SAP Signavio , How To