The Vault add-in for Pro/ENGINEER supports multiple workspaces. To use this feature, you must define a root-folder for all workspaces in your local environment.

You must have read and write access to the folder.
Once you have set up PRO_ADDIN_WORKSPACE, you can create subfolders under your main workspace folder and use them as multiple workspaces. You can set a default workspace using the PRO_ADDIN_ACTIVE_WORKSPACE Windows environment variable.