In vertical type, Alt+Down/Up (with or without Shift) steps kerning at a
caret or tracking of selected text, Alt+Left/Right steps leading, and
Alt+Shift+Right/Left steps baseline shift; Cmd/Ctrl makes five steps.
Horizontal type keeps its mapping. Selected type objects follow the same
rule when all of them are vertical, and a selection that mixes horizontal
and vertical type takes the horizontal mapping in one undo step.