This is not really related to suitescript.. does the REST API expose custom records? Like

Fixed Asset Depreciation Entry

for example? Which of course is not listed here https://system.netsuite.com/help/helpcenter/en_US/APIs/REST_API_Browser/record/v1/2024.1/index.html

yes, REST API exposes custom records, your URL will look like this: https://{{account}}.suitetalk.api.netsuite.com/services/rest/record/v1/customrecord_xxxx_xxxx_xxx

Thanks