Description:

Currently, there is no such feature in YAML specs using which we can configure 'finaltask' execution. This could be very useful as a lot of customers prefer YAML over Java.

H6.Workaround:
Use Java Specs to configure this.
Example:

Job job = new Job("Job", "JOB")
    .tasks(new VcsCheckoutTask()
        .addCheckoutOfDefaultRepository(), new ScriptTask()
        .fileFromPath("build.sh"))
    .finalTasks(new ScriptTask()
        .fileFromPath("cleanup.sh"));