text: Gantt view for task management - Software Recommendations Stack Exchange
  Having made some bad experience with my workload recently, I am looking for software to better visualise periods of heavy workload using sort of a Gantt view: A task in my Thunderbird lightning has a beginning and an end (deadline when it's due). I would like to quickly see at what time how many tasks and events are overlapping (within a range of weeks or months), so I can place new appointments and tasks in periods with more free time. This should work with my IMAP as well and visualise tasks I have in lightning. Preferably on Linux (Ubuntu). This is not supposed to be collaborative in any way, just for me.
  I am already using Gantt view for Thunderbird, but it does not seem to visualise tasks.
  asked Jun 14, 2018 at 19:53
  I am the developer of the Gantt View add-on for Thunderbird.
  It should display tasks in the Gantt view along with the calendar events. Please check the following:
  "Show tasks in view" option is selected - I think this is a lightning option, and may also be available under the View menu (I'm not on my pc at the moment so I'm going on memory here).
  Make sure that tasks have a valid start date and due date, so that it knows where to draw it.
  Once the task is visible, you can mark it complete by clicking on the task icon at the left of the bar. The progress bar will show the progress % which is set within the edit task dialog. You can drag/drop/stretch tasks just like events.
  Note, I have just released a new version for compatibility with Thunderbird 60 which I have tested thoroughly. This is still on the "beta" channel but should update automatically when that version is released.