As a Jira administrator you should be able to completely disable the Drag and drop subtasks feature

Problem Definition

Beginning with Jira 7.6.0 a new feature was introduced to allow for the re-arrangement of subtasks on a parent issue. See https://jira.atlassian.com/browse/JRASERVER-24547 and https://confluence.atlassian.com/jiracore/jira-core-7-6-x-release-notes-938027190.html#JIRACore7.6.xreleasenotes-other for details.

It is possible to disable the dragging of subtask through the use of a dark feature.

1. Login to Jira as an administrator
2. Navigate to $JIRAbaseURL /secure/SiteDarkFeatures!default.jspa
3. add the value of com.atlassian.jira.issuetable.draggable.disabled to the enable dark feature and click Add

However this will prevent the dragging of these subtasks both on the issue details page and through the issue navigator. BUT in the issue details view you will still see the up and down arrows that can be used to rearrange the order of these subtasks.

It appears that when using this specific dark feature to disable that draggable feature, the system is still imposing the up / down arrows on that page. Even though there exists another feature flag by the key of com.atlassian.jira.issuetable.move.links.hidden It appears that both disabling the dragging and hiding those icons can not be implemented at the same time within Jira.

Suggested Solution

Ultimately, we need a way to disable this feature in Jira. Possible solutions are to change the way the first feature flag works to completely disable the ability to change subtask order. Alternative to that would be to create a 3rd feature flag that accomplishes the same.

Why this is important

The problem with this is that since previous versions of Jira never allowed for this, some administrators actually created dependencies in regards to the number of subtasks an issue has and the sequence in which they appear on that issue. As such it is important to those Jira admins to maintain the old functionality that prevented end users from being able to change the order of these subtasks.