If you prefer to see the email under your Gmail subtab or see your Google docs sub tab on a custom record, you can ask your NetSuite Admin to follow these steps in order to enable the Gmail/GDrive subtab for your custom records:
Step 1: Navigate to Customization->Scripting->Scripts->List
Step 2: Search for “Celigo Gmail Gdocs Sub Tab”. Click ‘Edit’ next to the script.
Note : In some accounts you may not find the "Edit" button , in such cases you can click on "Deploy" button to make the suggested changes and then save.
Step 3: Under deployments, add the custom record types on which you want the Gmail/GDrive Subtab and click Save. And you should be able to see the Gmail/Gdrive subtab under your custom record type.
You need to have a valid GDrive license for the Gdrive subtab to appear on your NetSuite interface