Customize index of process names when published in web format

Hello Team.

Is there a way to customize index of process names when they are published in web. As of now it gets published as a list. What I want to achieve is to get them indented in a tree structure such that If there is a process hierarchy.

All L1 have "+" sign and there respective L2 can be expanded or collapsed using that. Please advise if such customization is possible at all and if yes how?