PICO-APL4 has variant to support eDP panel.   (PICO-APL4-A10-0002)
Please check   detail in AAEON homepage as following.
https://www.aaeon.com/en/p/pico-itx-boards-pico-apl4#downloads
Here is information about the eDP connector on the board.
It helps to  check cable  connection  for eDP Panel application.
CN19 on board with  KEL connector is for eDP output. (Board-Wire (Conn.30P.90D(F).0.5mm.SMD.KEL.SSL00-30L3)
Drawing under following link:
http://tinyurl.com/yyrbpdxs