If you are unable to apply custom fields in forms in NetSuite, you can try the following steps:
1. Check your NetSuite permissions: Make sure that you have the appropriate permissions to create and edit custom fields. Check with your NetSuite administrator if you’re not sure.
2. Ensure the custom fields are added to the form: Check that the custom fields you created are added to the form you are trying to edit. You can do this by going to the form layout customization screen and checking the fields tab.
3. Check for field-level restrictions: NetSuite allows you to set field-level restrictions on custom fields. Check that there are no restrictions that are preventing you from adding the custom field to the form.
4. Clear your browser cache: Sometimes browser cache can cause issues with NetSuite forms. Try clearing your cache and reloading the form builder.
5. Try a different browser: If the issue persists, try using a different browser to see if the issue is specific to the one you are using.