Unfortunately, there is no native function available in JIRA Cloud to do this. I haven't been able to find a Cloud add-on that can help. Maybe someone else in the community will be able to suggest something, better but...
..a possible workaround is JQL search ordered by sub-tasks, so that issues with no sub-tasks will show first in the results:
issuetype = Task ORDER BY subtasks DESC
Add the "Sub-tasks" column to your filter results so you can see which have none:
I found a couple of suggestions in Atlassian's public issue tracker that could be worth watching/voting on:
Hi there! Shannon from Statuspage here. 👋 With Cyber Monday quickly approaching, we're looking to hear from Atlassian customers – specifically from teams who touch incident response li...
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