Different columns in subfolder and Document Sets

[Hogne1260]

I have a customer who has wants me to do the following:

• Create a document library where the root folder has the standard columns
• Create two sub folders inside the root folder: Documentation and Reports
• Create a document set with two columns: Certifier and Due Date
• Create a third sub folder called Drawings, where the document set will be used
• Add the two columns from the document set to the Drawings folder

It's no problem adding those two columns to the Drawings folder. But: The Certifier and Due Date columns are also added to the root folder and all the other sub folders! Why?

I've googled until I was blue in the face on how to achieve this, but the closest I've gotten is a reply telling me that in old SharePoint, this was possible, but not in "modern" Sharepoint. 

Please, help! 

[#2]

@Hogne1260 Hi there, this is a few months old. Did you ever find a solution? I am attempting something very similar in SharePoint online with subfolders, each having different custom metadata columns. There is little to no information on how to do this, not to mention the constantly changing admin tools and menus make it difficult to find proper instructions in the first place. It almost seems as if we should create a separate document library for every "folder," which seems like a management and navigation nightmare.

[#3]

Is this functionality available yet?