Edit field value while converting task type

[Pooja Heda]

I have a situation here! My manager wants to have fix version in tasks/ stories/ bugs but not in subtasks (as its inherent from respective story's version) which is fine. But when a task need to be converted to subtask, now it shouldn't hold the fix version field value. 

Is there any way where we can edit the field value right at the time of converting it from task to subtask? 

I've been bulk editing such subtasks (as many times it happens that incorrect task type is created coz there are many users who create tasks) but it's a pain to always keep a check on such stuff. 

Any inputs would be really appreciated. Thanks in advance! 

[Nic Brough -Adaptavist-]

If you set the field configuration so that sub-tasks do not have the version field(s), then they will vanish when you convert an issue to a sub-task

[Pooja Heda]

Field configuration for subtasks is already not having fix version field. However, it's still being carried over when converted from task to subtask. I could see the subtask with versions in release versions. That's my pain point.