This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
瑝 combines 王 (jade/jewel) with 皇 (emperor, brilliant). The exact historical development is uncertain, but it likely relates to a type of jade or a brilliant gem.
The left side 王 suggests a jewel, and the right side 皇 suggests something brilliant or imperial. Picture a brilliant imperial jade ornament, though its exact meaning is uncertain.
For コウ, imagine a brilliant jewel glowing with a warm, golden light: the glow cues コウ, and the jewel (王) shines like an emperor's treasure (皇).