https://forum.flirc.tv/index.php?/topic/11418-any-way-to-get-the-json-for-device/&do=findComment&comment=29399 is where Jason advised how to do it with the flirc irtools.exe on Windows. I've had mixed success with it (sometimes the IR I capture just doesn't work) but certainly has helped me get a few missing buttons sorted. Hope this helps.