Unable to create, edit, or delete Apex triggers or classes in Salesforce

Only Developer Edition, Sandbox, and Trial organizations have the ability to create, edit, and delete Apex classes and triggers directly in the Salesforce CRM user interface. Unlimited Edition and Enterprise Edition production organizations can execute Apex and can view Apex in the user interface, but modifying Apex in the user interface is not allowed.

The Apex classes and triggers should first be written in a Developer Edition, Sandbox, or Trial organization along with the appropriate test methods that test at least 1% of triggers and 75% of classes. To deploy Apex into a production organization, a user with the Author Apex permission must deploy the triggers and classes using either the compileAndTest() or deploy() Metadata API methods which can be accessed with either the Apex Development Tool based on Apache ANT.

You can deploy Apex using:

• Change Sets
• Salesforce extensions for Visual Studio Code
• Ant Migration Tool
• SOAP API
• Third-party tools that use Metadata API or Tooling API
• VS Code with Salesforce DX plug-ins

Deploying Apex