(feature) have a tree-view for sub issues

[joaovl5]

Description of the issue

I'm suggesting a better way to visualize sub issues in the list view. Sub issues should appear as children of the parent issue, so it becomes a better way of keeping track of all tasks.

An example of such a feature is on Clickup:

[mcgurvy]

Current Problem:
In the current list view, sub-issues are displayed as individual items alongside parent issues. This can make it difficult to visually distinguish between parent tasks and their corresponding sub-issues, leading to a cluttered view and less efficient task management. Users might find it challenging to track the relationship between parent issues and their sub-issues.

Proposed Solution:
To enhance the clarity and usability of the list view, sub-issues should be displayed as "children" of their respective parent issues. This hierarchical visualization would indent sub-issues under their parent task, making the structure of tasks and sub-tasks more apparent. This approach ensures that users can more easily track the progress of each parent issue and its associated sub-issues in one glance.

Parent issues will appear as main entries.
Sub-issues will be indented beneath their respective parent issues.
Collapsible/expandable functionality could be added to further declutter the view, allowing users to expand or collapse the view of sub-issues under each parent.
Benefits:
Improved organization and visibility of tasks and sub-tasks.
Easier tracking of overall progress and relationships between issues.
Reduced visual clutter, leading to a more streamlined and user-friendly task management experience.