How do I save a favorite resolution without right-clicking?

Select the display mode you want, open Manage… beside Favorite modes, and click one of the five numbered slots. This saves the current mode in that slot. Favorite modes require Pro.

Open App Menu > [display] > Display Mode and select the desired mode first. If it is hidden, open Filter… and check the aspect ratio, refresh rate and HiDPI selections. See missing modes. A filter changes the list, not the active resolution.

For the rendering background, see how macOS scaling, HiDPI and LoDPI work.

Under Manage…, the row Assign current resolution to favorite: provides slots 1–5. Filled circles indicate occupied slots. Clicking an occupied slot replaces its saved mode with the currently active one, so choose an empty slot if you want to keep the existing favorite. Use the small × beneath an occupied slot to remove it.

You can also secondary-click a mode row and choose Set as Favorite for a slot. If secondary-clicking only selects the mode, use Manage… or check your mouse or trackpad’s secondary-click configuration in macOS.

A favorite stores a display mode, including its properties, rather than just a width and height. It does not make an unavailable combination supported. See Display Mode favorites for selecting and managing saved modes.