When I am notified of an edit in a dossier, how do I know what the edit was? Is there a way to drill into that?

You can see a summary of the changes in the comments section

When you are notified for a change into a Dossier, i.e. the Indonesian Food Regulatory Guide, you can have a summary of the changes by accessing the comments sections on the right panel as per the screenshot.
comments on dossiers
 
If you will create your own dossiers, every time you publish a new version, the system will ask you to enter comments about the changes, so you'll be able to track those changes too if you'll need to do so, else you can disable the commenting function.
Comments on Dossier