Role hierarchy explorer -- new feature "select the level you want to see"

[VinceFINET]

Is your feature request related to a problem? Please describe.
With very large hierarchy it is sometimes good to check only the first levels of the tree. so for instance i would like to be able to select the level i can see in the graph.

Describe the solution you'd like
Why not having a picklist that will have dynamically "All levels" (default value), "Level 1..2", "Level 1..3", etc... (depending on the depth of the current full tree.
Note that "Level 1..1" doesn't have any added value so i removed it from the list.
When selecting a value the graphic is re-calculated to only show the nodes of a specific level

Describe alternatives you've considered
No alternative

Additional context
N/A