Press E for edit mode. Hover the top-left for Edit, Pages, Save, then Undo / Redo / Done (exit). Ctrl+S also saves. Esc blurs text or exits. Ctrl+click multi-select. Drag ⠿ to move; drag corner to resize.
Second slide
Reorder or delete slides from the sidebar. Snap aligns to slide center and other objects — not the outer edges.
Third slide — click into text for the format bar (bold / italic / font / size).