Job, account and group 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).
Depending on whether you've enabled any of the advanced settings for groups, you may also be able to filter groups by group type here. If you've nested groups one within another (hierarchical groups), you'll have the option in this right-click popup for Parental independence. If checked, groups can be checked and un-checked without their parent (or children) being changed.
Right-click on any item in (most) of these lists to select All, None, or Reverse. Even better: in many cases you can see the definition/setup of any item by right-clicking on it from the open or closed list here, then selecting View.