I’ve been developing extensions for OpenCart for a long time and now I’m looking for something new to make modules too. Does your system allow you to integrate add-ons?
Welcome to the forums.
Yes ExpressionEngine allows 3rd party addons, they come in three types:
Plugins - small scripts that are called in templates to modify something
Extensions - scripts that use hooks to modify or enhance things but only in the control panel
Modules - scripts that add enhanced functionality, modules can have database tables, control panel fields (i.e. settings), and front end tags for output
Docs are at https://docs.expressionengine.com/latest/development/addon-setup-php-file.html
Currently available addons are listed at https://expressionengine.com/add-ons and https://devot-ee.com/