Crouch on the lowest stair, then shinespark horizontally to bonk at the top corner of the grapple block. Down grab to get onto it.

Entrance condition:

{
  "comeInShinecharged": {}
}

Requires:

{
  "shineChargeFrames": 110
}
{
  "notable": "Shinespark Down-Grab to the Grapple Blocks (Left to Top)"
}
"canSuitlessMaridia"
"h_canCrouchJumpDownGrab"
"canHorizontalShinespark"
{
  "shinespark": {
    "frames": 56,
    "excessFrames": 0
  }
}

Dev note: This is only done suitless, as with Gravity, you can gravity jump up there. A similar strat can be done from the top right door, but it doesn't have a nice setup and has to be done midair.