OpenCues adds exactly two axes to your keyboard. Horizontal (Ctrl+Alt+←/→) navigates: a highlight walks between the words that have something to offer. Vertical (Ctrl+Alt+↑/↓) cycles: the highlighted word swaps through its alternatives in place.
The highlight is not your cursor
Your caret stays wherever you were typing; the highlight is a separate selector, so you can browse alternatives mid-sentence without losing your place. Only words with something behind them are selectable: cued words, filled blanks, agent edits. Plain prose is skipped entirely.
Cycling is priority-ordered
What Up/Down does depends on what the highlighted word is: a settings selector swaps settings, a filled blank steps its value (volume actually changes), a word cue swaps synonyms, and an agent edit cycles back to your original text. One gesture, resolved by what's under the highlight.
Tuning it
The modifier is switchable between ctrl-alt (default everywhere) and ctrl-shift via the nav-keymap setting, for terminals that don't forward Ctrl+Alt. An opt-in cursor-navigate mode makes the highlight follow your caret into navigable words instead of being driven separately. On macOS, Ctrl+Option+Arrow works in most terminals; Terminal.app needs "Use Option as Meta key" enabled in its profile settings.
Related: What is a cue? · How OpenCues keeps your place · GitHub repo