When using a gdnconfig file to specify configuration settings, there is no option to enable the --soft-fail property.
That means the following error is shown in the output for the pipeline

If you set the configuration settings as env variables directly in the pipeline it seems to set soft-fail automatically and you dont see the error message. Below is an example of being able to set soft fail.
"tools": [
{
"tool": {
"name": "Checkov",
"version": "Latest"
},
"arguments": {
"DownloadExternalModules": "true",
"SkipCheck": "CKV_TF_1",
"Quiet": "true",
"SoftFail": "true"
}
}
]
}