Cannot remove custom EB environment variable

The issue you're experiencing with removing a custom environment variable in Elastic Beanstalk (EB) is not typical behavior for user-defined variables. Generally, custom environment variables can be added, modified, or removed as needed.

However, the error message suggests that the system is treating this particular variable as "required," which is unusual for a custom variable. This could be due to a few reasons:

1. The variable might be used in a critical configuration file or script within your application, and EB is detecting this dependency.

2. There could be a setting or configuration in your EB environment that is referencing this variable, making it appear as required to the system.

3. It's possible that there's a bug in the EB console or API causing this unexpected behavior.

To resolve this issue, you can try the following steps:

1. Use the EB CLI to view and modify your environment's configuration. Run 'eb config' to view the current configuration, locate the environment variable you want to remove, and set its value to null or delete the entire line containing the variable.

2. If the above doesn't work, you can try updating your environment using a saved configuration or .ebextensions configuration files that don't include the variable you want to remove.

3. As a last resort, you might need to create a new environment without the variable and then swap the environment URL with your current one.

If these steps don't resolve the issue, it would be advisable to contact AWS support for further assistance, as this behavior is not standard for custom environment variables in Elastic Beanstalk.

Remember to always test changes in a non-production environment first to ensure they don't negatively impact your application.
Sources
Setting configuration options after environment creation - AWS Elastic Beanstalk