There are two ways you can track a reread on The StoryGraph:
1. Track it in real time by changing the book's status to 'rereading' and track as normal:

Then move it back to 'read' when you're done and it'll be tracked as a reread. You should see something like this in the Activity section of the book page:

Then move it back to 'read' when you're done and it'll be tracked as a reread. You should see something like this in the Activity section of the book page:

2. Track your reread retroactively by going to the book page and clicking View/Edit Read History (behind the three-dot menu in the app). Then use this panel to add in the dates of your reread:
Rereads are displayed as separate entries in your read list.
To track a reread against a different edition, simply mark the edition you want as 'read' or 'currently reading' as normal. You'll still see the 'You have read this book 2 times' on both editions' pages. :-)
You can only leave one review per edition, so if you'd like to add a new review for your reread, we recommend editing your existing review and adding your new review below the old one.