[Enhancement] Vertically demonstrate dependency as a tree.

https://github.com/tasks/tasks/issues/1868#issue-1222154156 describes the request, whereas https://github.com/nextcloud/tasks/issues/2185#issue-1561309542 demonstrates the necessity of this.

Request

Many possible methods of easy demonstration of dependency exist, and each provides unique advantages.

Examples:

1. Tree

   Provides additional information whilst displaying relationships in an intuitive manner.

   Examples:

   1. GitKraken

      

      https://www.gitkraken.com/github-student-developer-pack-bundle

   2. Phabricator

      

2. Mindmap

   Conversely,

   <iframe src="https://anvaka.github.io/sayit/?query=tasks"></iframe> <!-- https://github.com/github/markup/issues/538#issuecomment-786402900 -->
   

   is able to demonstrate complex relation. However it does so without cohesive presentation of additional information, although a basic nested table

   flowchart TD
       A[Task] --> B[<b>Relation</b><br><table><tbody><tr><td><b>Attribute</b></td><td>Value</td></tr><tr><td><b>Attribute</b></td><td>Value</td></tr></tbody></table>]
       A --> C[<b>Relation</b><br><table><tbody><tr><td><b>Attribute</b></td><td>Value</td></tr><tr><td><b>Attribute</b></td><td>Value</td></tr></tbody></table>]
       B --> D[Relation]
       A --> E[Relation]
       B --> F[Relation]
       G[Relation] --> B
       A --> H[Relation]
   

   is not an infeasible manner of overcoming this barrier.

However, I believe that how Phabricator implemented this ability^0 is ideal (scroll to the Task Graph if your browser does not automatically) because it provides the advantages of the previous methods, yet provides intuitive vertical presentation of information, and retains the current list as the primary interface.

This is dependent upon implementation of https://github.com/tasks/tasks/issues/1867#issue-1222152770. It may be a duplicate of https://github.com/tasks/tasks/issues/452#issue-182067503, but I am not confident that it is.

Correlations

1. https://gitlab.com/gitlab-org/gitlab/-/issues/273597
2. https://gitlab.com/gitlab-org/gitlab/-/issues/29914
3. https://github.com/nextcloud/tasks/issues/2013 and
4. https://gitlab.com/gitlab-org/gitlab/-/issues/223035#note_931729947

Start by reviewing the linked issues 1867 and 452 to understand the dependency model and whether this request is a duplicate. Done means presenting task dependencies as an intuitive vertical tree while retaining the current list as the primary interface.