Simple UI mode
One toggle strips the editor to the essentials, hiding the extra toolbar groups, tool-window stripe, breadcrumb, gutter, and minimap for a calm, minimal surface.
One toggle strips the editor to the essentials (hiding the extra toolbar groups, the tool-window stripe, the breadcrumb, the entire gutter (line numbers, fold chevrons, and all markers), and the minimap) and turns off the heavier features (LSP, debugging, Git, multiple cursors) for a calm, minimal surface.
The menu bar stays, simplified rather than hidden — File, Edit, Find, View, Help. The menus that go are exactly the ones the mode switches off, which would otherwise sit there entirely greyed out. Toggling Simple mode stays in that reduced View menu, so it is never a one-way door for anyone who entered it from there.
Toggle it from Settings → Interface → Modes, the toolbar, the palette, or the --simple CLI flag (session-only). Toggling off restores everything exactly.