Account Hierarchy Using Tree Grid in LWC

skAccountHierarchyCmp.html

<template>
    <div>
        <lightning-card  title="Account Hierarcy">
            <lightning-tree-grid
                columns={gridColumns}
                data={gridData}
                key-field="Id"
                hide-checkbox-column="true"
                expanded-rows={currentExpandedRows}>
            </lightning-tree-grid>
        </lightning-card>
    </div>
</template>

skAccountHierarchyCmp.js

import { LightningElement,wire,api } from 'lwc';
import fetchAccounts from '@salesforce/apex/skAccountHierarchyCmpController.findAllHierarchyAccounts';
const COLLS = [
    {
        type: 'url',
        fieldName: 'AccountURL',
        label: 'Account Name',
        typeAttributes: {
            label: { fieldName: 'accountName' },
            target: '_self'
        }
    },
    {
        type: 'text',
        fieldName: 'Industry',
        label: 'Industry'
    },
    {
        type: 'text',
        fieldName: 'Type',
        label: 'Type'
    }
    
];
export default class SK_AccountHierarchyCmp extends LightningElement {
    gridColumns = COLLS;
    gridData = [];
    roles = {};
    currentExpandedRows=[];
    @api recordId;
    @api objectApiName;

    @wire(fetchAccounts, { recordId: '$recordId'})
    AllAccountInfo({ error, data }) {
        if (error) {
            console.error("error loading accounts", error);
        } else if (data) {
            //console.log('*****dat from apex:'+JSON.stringify(data));
            console.log('**ObjectAPI Name:'+this.objectApiName+'***current account Id:'+this.recordId);
            var finaldata=[];
            var expandedRowInfo=[];
            for ( var i = 0; i < data.length; i++ ) {
                if(data[i].ChildAccounts){
                    expandedRowInfo.push(data[i].Id);
                    this.roles[data[i].Id] = { 
                        accountName: data[i].Name ,
                        Id: data[i].Id, 
                        AccountURL:'/'+data[i].Id,
                        Type:data[i].Type?data[i].Type:'',
                        Industry:data[i].Industry?data[i].Industry:'',
                        _children: [] 
                    };
                }else{
                    this.roles[data[i].Id] = { 
                        accountName: data[i].Name ,
                        Id: data[i].Id, 
                        AccountURL:'/'+data[i].Id,
                        Type:data[i].Type?data[i].Type:'',
                        Industry:data[i].Industry?data[i].Industry:''
                    };
                }
            }

            for ( var i = 0; i < data.length; i++ ) {
                if(data[i].ParentId){
                    if(this.roles[data[i].ParentId]){
                        this.roles[data[i].ParentId]._children.push(this.roles[data[i].Id]); 
                    }
                }
            }
            //console.log('***after adding childrens :'+JSON.stringify(this.roles));
            for ( var i = 0; i < data.length; i++ ) {
                if(data[i].ParentId){}
                else{
                    finaldata.push(this.roles[data[i].Id]);
                }
            }
            console.log('***finaldata :'+JSON.stringify(finaldata));
            this.gridData=finaldata;
            this.currentExpandedRows=expandedRowInfo;
            console.log('***currentExpandedRows 2:'+JSON.stringify(this.currentExpandedRows));
        }
        
    }

}

skAccountHierarchyCmp.js-meta.xml

<?xml version="1.0" encoding="UTF-8"?>
<LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
    <apiVersion>55.0</apiVersion>
    <isExposed>true</isExposed>
    <targets>
        <target>lightning__RecordPage</target>
        <target>lightning__AppPage</target>
        <target>lightning__HomePage</target>
    </targets>
    <targetConfigs>
        <targetConfig targets="lightning__RecordPage">
            <property
                name="recordId"
                type="String"
                label="Record Id"
                description="Pass the page's record id to the component variable"
                default="{!recordId}" />
            <property
                name="objectApiName"
                type="String"
                label="Object Name"
                description="Pass the page's object name to the component variable"
                default="{!objectApiName}" />
        </targetConfig>
    </targetConfigs>
</LightningComponentBundle>

skAccountHierarchyCmpController.apex

public with sharing class skAccountHierarchyCmpController {
    @AuraEnabled(cacheable=true)
    public static list<Account> findAllHierarchyAccounts(string recordId){
        list<Account> allAccountList=new List<Account>();
        string ultimateAccountId;
        for(Account acc:[select id,Ultimate_Account_Id__c from Account where Id=:recordId]){
            ultimateAccountId=acc.Ultimate_Account_Id__c;
        }
        if(string.isNotBlank(ultimateAccountId)){
            for(Account acc:[select id,(select id from ChildAccounts),Name,ParentId,Type,Parent.Name,Industry 
            from Account where Ultimate_Account_Id__c=:ultimateAccountId order by parentId NULLS FIRST]){
                allAccountList.add(acc);
            }
        }
        system.debug('***allAccountList size:'+allAccountList);
        return allAccountList;
    }
}

Hello Sunil,
Created Ultimate_Account_Id__c and implemented this shared code. However, I am getting only one level, i.e., Parent.

could you please suggest , what am I missing here ? How to get remaining child and grandchild

Thank you very much !