Use CRM system

Configuration

Go to Settings > CRM

Add new Type and Group for CRM

Press New to add new CRM Custom Field

Save the changes

Enter the field Name, choose Type (use Type Text and Values Area to create dropdown with fixed values), enter Values if needed, choose Fields Group select areas to use the field (Contact, Company, Order, Supplier).

Save the changes

Registration fields

Go to Online Store > Settings

Open Registration tab, select a field you want to add to the website registration form, make it Required (optional) add a Description (optional)

Save the changes

Customer

Go to Customers > Search Customer

Search Customer

Find a Customer account and open it

You can access custom CRM fields for Company or for Contact

Orders

To open CRM Custom Fields in Order details window go to Notes tab, then Tags