It divides the close's move over the last window bars, as a fraction and without its sign, by the window's high-to-low range, also as a fraction. Near 1, price went mostly one way; near 0, it went back and forth. The line shows only where that ratio is above the threshold and is empty elsewhere; at the default 0.02 it shows on most bars.

How to read it

The line sits in its own pane; higher readings mean a cleaner one-way move.
Gaps mark bars at or below the threshold, where price went nowhere net over the window.
Readings can pass 1, because the start price sits just outside the window's range.

What it outputs

Trend efficiency: The net move over the window divided by its high-to-low range, shown only above the threshold.

Settings

window: How many bars the move and range are measured over. Longer windows judge the larger trend; shorter ones swing with each push.
threshold: The ratio below which a bar is left empty. Raising it, say to 0.5, keeps only clearly directional stretches.

Pitfalls

Despite its name it is a ratio line, not a yes/no regime flag: read the height, and treat gaps as not trending.