Low left-stem tone bar

It writes a low pitch on a five-level tone scale.

Many languages, Chinese among them, use pitch to tell words apart. In 1930 the linguist Yuen Ren Chao proposed drawing it: a vertical line is the speaker's pitch range, split into five levels from 1 (lowest) to 5 (highest), and a short bar shows where the voice sits. The IPA tone letters ˥ ˦ ˧ ˨ ˩ put that line on the right. ꜕ is the same low bar with the line on the left.

Why mirror it? In some Chinese linguistics the two sides separate two layers: the right-stem letter gives a syllable's own tone, the left-stem one the tone it really takes in a phrase after tone sandhi (a tone change caused by neighbouring syllables). Written ˧꜕, a syllable is mid by nature but comes out low. Each author's notation key confirms the exact use.

How do I type it?

No keyboard has it; use a character picker or its code.

꜕ is a full character that takes its own space after the syllable, not an accent over a letter. Fonts that support phonetic symbols may join tone letters in a row into a single contour line, which is intended.