Gantt app from tasks to issues

[ITManager]

Hi, 

I am searching for an app for project planning ( where I can draft tasks, dependencies, early starts, ends, and whatever, independently from any JIRA projects.

Then, only when everything is ready, convert GANTT task and subtask in JIRA EPIC issues and JIRA task/story issues.  

Is there anybody out there able to address me? 

best, 

Alessandro

[Nic Brough -Adaptavist-]

Issues are the heart of Jira and everything in the software is about tracking them.

There simply isn't an app that is completely independent of issues for Jira. 

The closest I can get is "Advanced Roadmaps" which at least allows for lots of "we don't yet know how big X is" when you use it to plan things.