The Tools menu is always available from the main window menu bar and groups together the commands used less often than day-to-day mail actions:
Ctrl+Shift+B)Ctrl+Shift+L) — opens the Rules Manager.Ctrl+Shift+P)Choosing how QuickMail looks and reads is on the View menu, not here — Manage Themes… opens the Theme Manager, Density sets message list density, and Message List Fields… opens the field chooser. Next Theme and Previous Theme have no menu items; run them from the Command Palette, or give them a key of your own in File → Settings → Keyboard Shortcuts.