This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
懬 combines 廣 (broad, wide) with 心 (heart/mind). The exact historical development is uncertain, but it likely expresses a broad or expansive state of mind.
The outer part 廣 suggests something broad or wide, and the inner 心 is the heart. Imagine a heart so broad it can hold vast feelings, but since the meaning is uncertain, treat this as a visual hint only.
For コウ, picture a broad 廣 heart 心 that can hold a huge crowd: crowd -> コウ, and the broad heart welcomes everyone.