So I couldn’t find a solution and reached out the support and they provided me with one.
Turned out that there is no straightforward solution, so it was proposed to create one extra task, which is triggered from the error pipeline by ‘REST get’ snap when an error occurs in a child and runs some pipeline that always fails, like generation of an improper JSON with “JSON Generator” snap.
In this way, that extra task fails and sends notification.
As the result, I can use “Pipeline Execute” instead of “Task Execute” in the parent pipeline for triggering the child pipelines.
