How to make side menu work as accordion when click category

I work on angular 7 app I face Issue I can't make left side menu work as accordion .

meaning I need when open component report category on load display all categories for all reports

then when user select specific category then it will display sub category reports related by collapse it

so in stackbliz already display data For Category and Sub category but I need it accordion .

stackbliz below have only one component name report category that have left side menu

and service name display report service that have function service and data returned .

https://stackblitz.com/edit/create-1arrvm?file=app%2Fdisplayreport.service.ts