Good question here. Can we use any NetSuite web services features to save files into the FILE CABINET? Without any SuiteScript development?

wrong place for a non suitescript solution

I've been on here for years. Since 2017. How about you?

Thx @battk

In addition to using SuiteTalk, a Suitelet is a good place to upload files. You can also use SFTP to pull files in. Or you can even use the native Online Customer Forms if you want. There are a few ways to do this.