Problem: Currently, you can only view Stories and top-level tasks/bugs on the board. If an task or bug is a sub-item of a story, you can see it on the board. If a task/bug is a sub-item of another task or bug... you don't see it on the board. I'd like to see this changed, and I have specific ideas on the best way to do it.
What I LOVE about current features: If a task/bug is a sub-item of a story, you can move it across statuses WITHOUT moving the story itself. Even better - that task/bug, which is in a different status on the board, has a ghost/outline of the story it belongs to! Not only can I move sub-tasks/bugs around independent of their story, but I can EASILY keep track of what story it belongs to visually, at-a-glance, without having to view its details!
Now - what I wish would improve: Do the same thing for a sub-item of a task/bug! You could nest the ghost/outline of the task/bug right inside the ghost/outline of the story, making it very easy to track what's what. The whole idea of Agile is to keep things simple, so I honestly don't think most people will go any deeper than story -> task -> sub-item.
If you think this would become too cluttered/difficult, then why not at least allow it only from the story swimlane? There, you're viewing a whole story in a swimlane, so nothing is being nested anymore. Since we no longer need the story ghost/outline in this image... why not allow it with task/sub-task? or task/sub-bug? or bug/sub-task?
Honestly... if you could have cross-project boards/sprints, this would be completely unnecessary, BUT if Zoho is never going to do cross-project boards & sprints... then I think this is a very worthwhile and important feature to implement. (PS - look at the feature-set JIRA allows... Zoho should take its cues from that, as they're a leader in the Agile space).