Can I keep the other menu items visible while Display Mode is expanded?

Yes. Open Settings > Menu > Menu Appearance & Behavior > Additional Menu Options… and turn off Hide other unexpanded menu items under Expanding Menu Items.

When submenus expand inside the app menu, opening Display Mode normally hides other items for that display. Turning this option off keeps those items visible. This helps you use other adjustments while Display Mode stays open.

See Menu Appearance & Behavior for related choices, including whether expanded content stays open the next time you open the App Menu.