Can I choose scaling as a percentage instead of a resolution?

Yes. Enable Use magnification slider instead of resolution slider under Settings > Menu. This makes the resolution slider express interface size relative to the display's native size: higher magnification means larger interface elements and less desktop space.

Keep Show percentage for scalable displays enabled. Percentage presentation also requires Only resolutions that match native aspect ratio and at least twelve eligible slider resolutions. If the display has too few sizes, enable flexible scaling where supported. Flexible scaling requires Pro.

For the rendering background and a practical comparison, see choosing a comfortable macOS scaling mode.

The slider still selects an available display mode. Changing its presentation does not create modes or guarantee an exact percentage such as 125%. The label remains Resolution, with a magnifying-glass icon indicating magnification mode. Virtual screens use a size derived from their available modes as the reference.

Choose a HiDPI mode where available for sharper interface rendering. The logical desktop size, rendering size and physical output resolution are different quantities. A smaller logical desktop does not by itself mean that the monitor receives a lower-resolution signal. This scales the overall desktop, rather than independently resizing only a menu bar or an application's image canvas.

See Resolution Controls for filtering and percentage behavior, and HiDPI for how desktop size relates to rendering pixels.