Dear operationsmanager,
Greetings! Thank you for posting in Microsoft Community.
I'd like to help you. I went through your post. Since you post this question in OneDrive, I suppose you want to set up a file directory for a company by using OneDrive.
If so, as far as I know, OneDrive is primarily a personal cloud storage service for individuals, each user has their own OneDrive account. Users can store personal files in their OneDrive and share files and folders with others.
I recommend you use SharePoint because SharePoint is a collaboration platform for teams and organizations, it allows teams to collaborate on documents, lists, and other content in a centralized location.
Here is an article for reference: Should I save files to OneDrive or SharePoint? - Microsoft Support
To set up a file directory in SharePoint, you may create a SharePoint team site, then create a document library for each department, create 3 folders in each library.
Note: create a private SharePoint site, DO NOT add any users to it.
In document library, you may set up unique permissions at folder level for each folder: Top, MAIN, SHARE.
Here are detailed steps:
- TOP - access only for a CEO and the Head of department:
a. Go to the folder's permission page via selecting the folder and click Manage Access > click Advanced.
b. Then click Stop Inheriting Permissions from ribbon.
c. Then click Grant Permissions, enter name of CEO and the Head of department, assign a permission level and click Share.



- MAIN - access only for the Head and employees of this exact department
Use same steps as above, when Grant Permissions, you need to share with the Head and employees.
- SHARE - access for everyone in the company
Use same steps as above, when Grant Permissions, you need to share with everyone in the company.
Here is an article for reference:
Customize permissions for a SharePoint list or library - Microsoft Support
I hope above helps!
If my understanding of the scenario is not consistent with yours, or if you still want to set up a file directory in OneDrive, feel free to let me know, I will continue helping you.
Thanks for your time and understanding! Hope you have a nice day, stay safe and healthy always.
Sincerely,
Tina | Microsoft Community Moderator