Hi @abdulazizh,
If your script works as expected, post-processing should work as well. You cannot run any command on the closed incidents. If you want to test before implementing it, I would recommend having another pre-process rule for fake alerts and doing the testing on those ones by triggering some fake alerts on Splunk. I could not reproduce the issue due to the lack of Splunk integration, but Slack notification with incident details worked. So, you need to make sure the below command works as expected.
demisto.executeCommand("splunk-notable-event-edit", {"eventIDs": EID,'owner': user, "comment": nota ,"status":"5" })
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