Problem Statement:

As of today, the Convert to Issue/Sub Task operation cannot be restricted to user, groups, issue types.

Suggested Solution:

It could be possible to restrict it by:

1. Groups, i.e. only specific uses to be able to run this operation using project permission scheme
2. Issue Types, i.e. we would like to restrict the conversion to specific issue types.
   For example:
   1. Block Bugs to be converted to Sub-task, etc.