It would be nice if there was someway of specifying sub-tasks for a task (or you could call it a summary of many tasks)
start summary [big task]
[first part] for 10 days
then [more tests] for 2 days
then [check documentation] for 5 days
[first part] -> [more code]
This would then add a "task" bar on the top from which [first task] would start and would expand over all tasks.
Something similar to this image: https://img.officetimeline.com/website/Content/images/gallery/gantt-chart-project-management.png