Office 365 need to grant a second user as Publishing Editor for all of my inbox folders

I am an Office 365 user and have about ten folders, where each have a very large number of subfolders. I always thought that having subfolders was a good idea, until I now need to grant a second user with Publishing Editor permissions. Across these 8 to 10 folders, there are hundreds and probably thousands of subfolders, and my only option seems to be to do them one at a time, or through some type of PowerShell Script that I cannot get to work. My understanding is that once I get this done, that new subfolders will automatically inherit the permissions of their parent folder. If that is true, then I only need to get this done once. Is that true? I need some help. I have attached an image that is an example of how my subfolders are created. The folder structure goes 4 to 5 levels deep, so this would need to recursively done through some type of process.