Normal list to cascade list by behavior

[Ruslan]

Hello, exprerts. 

We have a custom field, which is filled from a post request to another system.

We get a list of elements and showing them. All this is implemented with the help of behavior.

The question is, is it possible to make a nested, cascading list. When hovering over an element, to open a tree of nested elements? if yes,maybe you have example.