Thanks for making this. Maintaining parity between Google Sheets Gantt charts and JIRA tickets is a real problem I have and one that is underserved by existing tools.
On the other hand this is a cursed development methodology. There's an infinite mine of No True Scotsmans about Agile, but really, when you find yourself putting your Agile stories in a Gantt chart and projecting sprints several months out, you are unambiguously rejecting substantive principle and content of Agile as a methodology. At this point it would be much more productive to admit that you're doing waterfall and put some effort into doing it well, instead of farting around with backlog grooming, sprint planning, etc. where the outcomes are all committed before the meeting in a master schedule.