Job and account drop-down editors and checklists normally display in a hierarchical fashion, that is, each job nested within its job group, and each account under its account type. Sometimes this is not intuitive to use, or you may not know which job group a job is under, or what type of account an account is under.
Right-click on any of these types of editors to choose Show flat (jobs and accounts) or Show by account number (accounts only).