Created Custom Field is not showing in the column chooser for Test Details
After creating the custom field in the Manage apps section of Jira, the second step is to enable the custom field for the individual project.
Go to the Jira project
Click in the Squad menu and scroll to the bottom and you'll see "custom fields"
On this page is where you can enable or disable custom fields on the project level:
After you've enabled it in the project, you'll then see it in the column chooser on the test case