Parallel execution should be enabled or can be switch on the fly in script console. Via a variable, similar to OctopusBypassDeploymentMutex

With the scenario that there is a process running (read: stuck/looping) in the target and executing a kill command via the script console will get you “waiting for script to finish in task…” so it is currently not the workaround.

Ref case:
https://help.octopus.com/t/force-stop-a-step-execution/26682/3