VSCode BPMN editor extension shows empty list on called element of a reusable sub-process node

Summary
We design two .bpmn process which belongs to same project and same package in VSCode. In one of the .bpmn, we add a reusable sub-process node. In the properties panel, the "called element" shows an empty list.

Goal
Populate sub-process Called Element dropdown with BPMN processes available on the opened folder (workspace) in vscode.