[AFAICS, there's no open task for this upstream, but if there is please correct me.]

In task views, there can be a quite complex list of tasks. For projects which use milestones, it would be great if they could be labelled with which milestone each task is in. This way you can see at a glance that a task is blocked by things which are in later milestones, and decide either to move this task to a later milestone or bring the sub-task sooner. This would be hugely helpful for complicated multi-milestone projects with lots of tasks.

For example, on T278547 which is in milestone Phase δ, I've created a new sub-task, T279679. It'd be great if I could see in task view mode that this is a blocker to Phase δ, and so know I need to do this in that milestone too.