Depending on your settings, competency elements may have a Ready for Versioning property you can enable to let the system track a previous definition of a competency each time you save your changes. Version numbers increment by 1 (beginning with version 1). Competency version information can show every element in the competency structure except activities.
Currently you cannot edit previous competency versions, however, your organization might want to track competency versions to review past changes to a competency structure's definition.
If you do not see the Ready for Versioning check box, ask your organization's administrator to enable the configuration variable d2l.Tools.Competencies.Settings.ShowVersionNumber.