Yes, you can edit your release while it's still processing, before it has been sent to stores.
On the Ditto Dashboard: head to your the Music tab in your Ditto dashboard and scroll down to Your Releases. Hover over the release you'd like to edit and hit the Edit icon button.
On the Ditto Mobile App: go to the Music tab (vinyl icon) and tap the release you'd like to edit.
Please keep in mind that you will lose your place in the release processing queue if you start editing a release while it is being processed. You will have to resubmit your release through the checkout and may also have to change your release date.