Watch the right-side standing pirate walk towards the wall as far as possible from below. The available running space is just enough to jump up and walljump the ledge by the door.

Requires:

"HiJump"
"SpeedBooster"
"canTrickyJump"
"canWalljump"

Dev note: This is also possible without going below and manipulating the camera, by standing on the slope and carefully jumping up and back.