The scale editor: imperial or metric, the presets, separate horizontal and vertical.
The scale editor is one control used in two places, page settings and layer settings. What it offers is the same in both.

A toggle at the top switches the whole editor, and the equation row below changes with it.
Pick the equation rather than typing it. Anything the presets do not cover can be typed straight into the equation row.
| Tab | Reads as | Values |
|---|---|---|
| Architectural | 1/4" = 1' | 3", 1-1/2", 1", 3/4", 1/2", 3/8", 1/4", 3/16", 1/8", 3/32", 1/16", 1/32" |
| Engineering | 1" = 40' | 10, 20, 25, 30, 40, 50, 60, 80, 100 feet |
| Metric | 1:100 | 1:50, 1:100, 1:200, 1:250, 1:500, 1:1000, 1:2000 |
The tab you were last on is remembered, so a civil estimator who lives in the Engineering tab does not land on Architectural every time.
Normally one scale covers both directions and the vertical follows the horizontal. Turning the option on reveals a second row set independently. It is for drawings genuinely stretched in one direction: a profile or section where the vertical is exaggerated to make grades readable.
Do not reach for it to correct a sheet that just prints slightly off; calibrate instead.