Being able to quickly see the difference between two Deployments is a great start when debugging a problem. From the difference, you can immediately see what changed and from that identify which elements to look into first in your attempt to figure out why things are not working.
You can create a diff between two Deployments from the App Details Screen.
Click on the three dots next to the Deployment you want to diff with another Deployment.
Select Diff deployment.
In the overlay window:
Select the Deployment that you want to compare with.
The diff will be shown in the overlay window.
You can create a new Draft from the diff by clicking on Create draft from the diff and send it to one of your existing Environments.