How should I record outstanding expenses in GnuCash?

[absconditus absconditus]

By 'outstanding expenses,' I mean bills that are due but that you
cannot, at present, pay. Nor do you know exactly when in the future
you would be able to pay.

Here's what I've experimented with:

I have created a new liability account ('TEST') with an opening
balance equal to the amount of the bill. I dated this initial
transaction to when I was supposed to pay the bill.

So far so good. Recording the bill's payment is what I find difficult.
To record the transaction, I have credited the 'Cash in Wallet'
account, and debited the 'TEST' account.

The problem is this bypasses the 'Expense' account. Ideally, I would
like for the bill-payment transaction to show as an expense. Also, I
thought the only way to modify Balance Sheet Accounts is through
Income and Expense Accounts.

The ability to account for outstanding expenses is very useful for budgeting.

Example:

The cable bill was due to be paid on 01/09/2014, but I could not pay
it back then. I cannot record it as an Expense-transaction with a
future data, because I do not know when I will be able to pay.

Many thanks in advance, absconditus