That should be possible using an Issue Security Scheme which will need to be configured on each of the Sub Tasks.
More info on Issue Security Schemes can be found on Atlassian's Confluence: https://confluence.atlassian.com/display/JIRA/Configuring+Issue-level+Security
Badges are a great way to show off community activity, whether you’re a newbie or a Champion.Learn more
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG