It is possible to go back change the status of your plan review after you have completed it. However, this can only be done either while the current review round it's still underway by pressing the 'More' button and selecting 'Change Result', or by initiating a Plan Revision if the plans are already approved.
As an example: the below review cannot be changed using the More -> Change Result option because both reviewers have already completed their reviews, meaning the current round is completed. To update the review, the best course of action is to perform a Plan Set Revision - please check our Plan Set Revisions Help Center article here for more information!
On a different example, either review can be changed because the review round is still underway as one of the reviews is yet to be completed:
Also worth noting that, once a Plan Review workflow step is completed, it cannot be resumed or changed. If you need additional review after completion, you'll need to either add another Plan Review workflow step to perform the necessary review work, or start a Plan Revision.
💡 Would you like to learn how to edit the workflow of an application? Check this article out!