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.
Thank you for suggestions.