By default, when you are in your OneDrive, the New Document button only has Document under it. This is great if you primarily create Word documents but you can add in Excel, PowerPoint and other content types.
It’s a straightforward process outlined here on the Microsoft site. You have to:
1. create your default template – so customize how it acts, default fonts, whether or not to show the ribbon, etc. – and save it as the template format for your program. That’s probably familiar – .potx for PowerPoint, .xltx for Excel – and OneNote needs an exported notebook package (.onepkg).
2. Follow the instructions on how to first add the content types to your site library, uploading the templates you just created.
3. Going to your OneDrive and adding your new Site content types to your OneDrive content types list. You can also reorder this list so your most used documents are at the top.
When you’re finished, you’ll have additional functions on your New Document button.
If you have created your own Document Information Panel, you want to link it when you’re creating your own template. That way, when you open the template, it loads the proper properties so that you can save the new file. It looks like you’re supposed to be able to add a custom document panel through the content types but when I tried to link it there, the templates stopped opening. You can edit your templates (normal.dotx, etc.) in place in your SharePoint/personal/your_username/Forms folder and subfolders.