Using diagram history feature, users can quickly review and restore diagram changes. If diagram uses new SVG format (cloud plugin as of late 2022) users will be able to easily restore that version.
By clicking the history button, user will be presented with the following popup:
History Explorer popup
When selecting version, Restore button will become active if valid info is found in that PlantUML SVG file. By clicking it, user will restore that version into editor. If version cannot be restored, only preview is shown and button is disabled.
If file does not use new SVG format user will not be able to go through file history. This is case with old diagrams that are created before new SVG format is introduced.
This diagram uses old file format
After you create new version for this file it will be shown in History Explorer but old versions will be omitted.
Server/DC versions also have History Explorer but are only able to show preview of the previous versions.