Sascha (gray ace) in To Love the Dragon King
Faelen (demisexual) in The Merchant's Love
Edmund (demisexual) in A Dance of Water and Air and A Harmony of Fire and Earth
Supporting characters:
Romilly (demisexual) in To Love the Dragon King and The Envoy's Honor. (Romilly is Sascha's cousin and an envoy of the king of Ivria. Their demisexuality is mentioned on page, though not explored in any depth. Romilly will have their own book, planned as book four of the Dragons of Ivria series. Look for them in To Know a Dragon Spy, the second Dragons of Ivria book when it releases too!)
Adora (gray ace) in the Chronicles of Tournai series. (Adora is the sister of Amory, one of the main characters of The Prince's Consort, and pops up in several books in the series, but primarily The Scholar's Heart and The Merchant's Love. Her asexuality isn't really mentioned on page yet. The series is on hold at the moment, but when I get back to it, her book is likely next.)
Briallen (asexual) in A Harmony of Fire and Earth. (Briallen is the sister of Rhys, one of the main characters. Her asexuality isn't explained on page, though it's perhaps implied. I'd like to return to this world and write a story for her, but she hasn't told me what she wants it to be yet!)