If you end or archive an experiment, the variations that have been created are still present in the backend for that particular landing page. They are part of the landing page itself even if you do not see them in other parts of the platform or on the live URL.
To resume your work right where you left off, simply create a new experiment for the same landing page and you will see the past variations populated in the new draft.
What about an existing experiment?
The case above applies to situations where you want to recover variations from an Experiment that was ended or archived. In case you have an existing experiment where you deleted one or two variations and you want those back, alongside the ones that were not deleted, then you can use the History tab on the right side of the page editor. Restoring the entire landing page to a version number that included those variations will bring them back.
Make sure that your experiment is not running when you do this. If it is, end it, then go to the editor for the landing page. On the right-side menu, you will find the History tab at the bottom. Click on it and restore the page version that had your deleted variation(s). Then, create a new experiment for the same landing page and you should see the deleted variation back in the list.
A new save version is created in the History section for each click of the Save button for any of the variations, as all of them are part of the same landing page and the History section is for the entire page.