Customizing "New" Button Functionality in SharePoint Document Library Across Different Levels

Hello everyone,

I'm currently working on setting up a new SharePoint document library and am facing a challenge in customizing the "New" button's functionality at different hierarchical levels. Here's what I aim to achieve:

1. Top Level - Customer: At this level, clicking the "New" button should allow the creation of a new folder. This folder will represent a customer, and I need it to fill in only one column, specifically the 'Name' column.

2. Second Level - Project: Within each customer folder, I want to create another level of folders for projects. When clicking the "New" button at this level, it should enable the creation of a project folder. For these folders, I'd like to have two columns filled out: 'Order Number' and 'Description'.

3. Third Level - Individual Files: Inside each project folder, I want the "New" button to provide the option to create documents based on predefined templates. There will be two different document templates to choose from.

My question to the community is: How can I customize the "New" button to behave differently at each of these levels? Any guidance on setting this up or pointing me towards relevant resources or documentation would be greatly appreciated! 

Thanks in advance for your help!