The breakage deposit should not be categorized as revenue, because you have undertaken no economic activity to earn it. Likewise, returning the deposit is not actually an expense. It is merely satisfying the liability. What I would do is:
Create a liabilities account called
Create the new customer identity, if necessary.
When you create a sales invoice, include a line for the deposit and allocate only that line to the
Breakage Deposits account. Allocate other lines according to what type of sale they are.
Using a journal entry, transfer the deposit to
Customer credits for that customer. Debit
Breakage Deposits and credit
Bank Accounts, Receive Money against that invoice in
Accounts Receivable. This can be done all at once, if the customer pays in full, or in stages.
When the chairs are returned from rental, Spend Money from the bank account, allocating the expenditure to Customer credits and the appropriate customer.
Unfortunately, as you have observed, you cannot allocate a sales invoice line item directly to
Customer credits. If you could, steps #1 and #2 above would not be necessary. I have raised this issue with @lubos before, but without response. This is the same situation as when a customer pays a deposit against upcoming delivery of goods or services, but requires a sales invoice in order to authorize payment. The small change of allowing allocation of sales invoice lines to
Customer credits would greatly streamline the workflow.
An important consideration here is that Manager’s present restriction requires creation of a liabilities account that you expect to be zero. Much better to hold amounts owed to customers in their individual
Customer credits subaccounts than to leave them lumped together in the temporary liabilities account where they are nameless.