This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 昒 is uncertain. It visually combines 日 (sun) and 勿, but the original semantic and phonetic roles are unclear.
The sun 日 beside 勿 suggests a time of day, but the exact meaning is unclear. Picture a dim, uncertain dawn when the sun is barely visible.
For コツ, imagine the sun 日 barely peeking through a thick fog, and you hear a soft 'kotsu' sound as a stone taps against a lantern in the early morning mist.