Hierarchical representation of TOC in report

rdata

Hello. I apologize if the problem have been discussed in other topic. I was wondering if there is a way to create a custom TOC in which the entries are represented as hierarchical tree, without using nested tables. The hierarchy is kept in a global parameter as a parent -> children HashMap object. Is there a way to create such a TOC and add it to the report ?
Thank you for your reply !

P.S. I started by using TOCBuilder and TOCEntry object in a custom java class, but did not succeed.