I use ProductBoard. It's fairly expensive but pretty great. I gather requirements into PB and use the inbuilt editor to flesh them out. When a story is ready I

I use ProductBoard. It's fairly expensive but pretty great. I gather requirements into PB and use the inbuilt editor to flesh them out. When a story is ready I push a button and it ends up in Trello (but you can add your own integrations; there's one for github for example). The integrations aren't perfect but I love it. Used it in my last job and brought it in at my current job. https://productboard.com https://productboard.com