You can version a project in the repository without adding the project to the Workbench.
Tip: You can browse existing versions of your project by clicking on the Details button in the Tag Resources dialog. Clicking Refresh from Repository should populate the Existing Versions list. It is sometimes helpful to see existing versions before naming your new version.
Tip: If the version tag you wish to apply already exists on some of the resources to be versioned, you can perform a Tag with Existing instead. This operation will move an existing tag to the selected resources and can be used to move both version and branch tags. If the tag you wish to apply is not show in the list, you can click Refresh from Repository. If this doesn't find the tag, you can click Configure Tags which opens a dialog that allows you to search for tags on specific files in the repository.