The new diary entry UI has the diary entry as a choice menu. This is pretty interesting. I think I like it. But...
But I would like to split some of these off as sub-tasks. Thus, for example, when viewing the "activity journal;" report, it would be nice to click on a diary entry, and bring up a menu that says "convert this to a task", and it would create a brand new sub-task, and move that diary entry, to it. (filling in the notes and title areas by copying the diary entry). This "promotes" a diary entry into a task.
Likewise, it should be possible to demote a task to a diary entry. e.g. in the journal, which shows the main project, and its sub-tasks, a pop-up menu should allow you to take an existing sub-task, and demote it into a mere diary entry of the main task.
I'm not sure, but maybe "promotion" is one way of preventing the diary entry menu from getting too big ... instead of deleting diary entries, one could promote them to sub-tasks, and then mark them as "completed", and that way, they'd not ever be visible again (assuming we hide tasks that are marked complete).