Yes, you should be able to do that by initiating the workflow (or a transition) based on a saved search. In either case, you would use a transaction search, type = Journal Entry and Account = Bad debt expense. You could either use that search for a scheduled workflow, and then have the entry state send the email. That would run every 30 minutes or so and send emails for all the matching transactions. You would probably want to set a field on the journal entry to indicate you had notified on it then filter those out from the search. Or you could have the workflow initiate on all journal entries, then use the saved search to cause an after submit transition to a state that sends the email, and then the workflow exits so you wouldn’t get duplicate emails.
Hope that helps…