You could hit the REST endpoint for approvals. (https://docs.splunk.com/Documentation/SOARonprem/6.2.1/PlatformAPI/RESTApproval) Unfortunately the docs do not include the POST requests for actually approving the task, so you'll have to do an approval in the web interface and then log the POST request using your browser dev tools.
Then you can use that POST request to approve tasks without having to log into SOAR. You will need to provide authentication credentials or a token though.
