Regarding the Goold Old Fantastic Analytic report in Odoo 15 which did what i wanted with the representation of Analytic Account Groups Parent/Child Feature 

My Project Budget 

Now I can't replicate the same output in Odoo 16 Analytic Plans Parent/Child because there is no dedicated Analytic Report to show them i can only find it in the P&L and it just adds a column to the report without the hierarchical view.

I tried the pivot on analytic items it does well but not exactly like it

I also tired the pivot on Budget analysis but it does'nt show the child plans and their subtotals

I even tired the new Horizontal Groups but it's not meant for Analytic Accounts its for the Accounts.