What this extension does:
This extension adds a copy of the standard "Category" module with unlimited (managed) nesting.

Features:

• Displaying a list of categories with unlimited nesting;
  
• Support for counting the number of products;
  
• No core files are changed or replaced;
  
• Output part of the categories or all at once;
  
• Control the display of inactive subcategory lists.

Demo:
Front:
https://oc4.secretsergey.com/en-gb/catalog/component/monitor/test-1
Admin:
https://oc4.secretsergey.com/admin/
Username: demo
Password: demo

How to install (4.x):

1. Login to your OpenCart Administration panel;
   
2. Go to Extensions > Installer and upload zip file suited for your OpenCart version;
   
3. After successful installation, find the extension in the list below and install it;
   
4. Go to Extension -> Extensions and select "Modules" on dropdown list;
   
5. Find the extension in the list below and install it;
   
6. Configure the extension and save the settings;
   
7. Go to Design > Layouts and add the module to the desired layout.

Support:
Email - sergey@secretsergey.com
Telegram - t.me/secretsergey
This extension is free and distributed "as is". Support for free extensions is paid.

I will be grateful for the evaluation and feedback on the extension page.
Thanks for your choice!