Same with other things like property taxes, house maintenance etc.

Home Expenses does this now (Maintenance, Improvements, Insurance, Real Estate Taxes).
I could see it being useful for other categories like medical (Health Insurance, Dental, Vision, deductible/out-of-pocket expenses).

It could display just like Home Expenses, so you could group related expenses or not in the chart options.

So maybe the feature is an Expense Group, which would let you add sub expenses like we do now for Home Expenses.

Yes, would love this too. Right now I keep a separate Numbers spreadsheet with individual categories and subtotals, so I can remember what is included in each main Expense in PL.

This is really needed. Look at Boldin for a good example.

Some type of hierarchy would be a nice feature as well. Allow me to create one expense called Living or Non Discretionary expenses but allow me to drill down or open up this expense to see individual expenses but keep them consolidated in a high level view like in cash flow.