In VSCode... is there a way to set a default setting for this, for deploying?

Doesn't look like it. I don't see any env variables that can be used to override it in the code. I think NetSuite would say probably say to use the CLI if you want to automate.

You can automate it using the CLI, so maybe setup a custom task to execute the cli command instead of using the SuiteCloud extension? Still seems like a settings option which could/should be added. use

--accountspecificvalues WARNING

in your CLI command to force warning, cancel is the default method.