If you need to change the temperatures or timing of your brew you can do via the tools section on the top right hand corner of the app.
There is a menu item called ‘edit stage time or temp’ indicated by a pencil icon in each step.
You won’t, however, be able to change any ingredients used in the brew session.
You will need to edit the recipe on the recipe creator and then restart the brew session.
If you edit the recipe on the app, the changes will be immediately available to the brew session, if you edit the recipe on the website, you will need to sync the changes to the app before they will be reflected in the brew session.