The main parts
The The Tree view is composed by two parts: the action tool barmenu bar and the tree view area.:
The menu bar
It groups some actions under the main buttons:
- the Filters for issues and links data
- the Auto-expand/collapse one entire level actions
- the More… menu with additional capabilities
By default, the first level is automatically loaded and expanded: Depth: 1
The issues are painted with white color for the background and their links children are grouped by link type with gray background color: 
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