Thanks for the screenshot, Masamune! We checked this spot closely. The mushroom island on the far right of Western Versal Forest <4> really is a little too high to reach by jumping from the floor beneath it. A normal jump tops out about 5 pixels short, and that is how this forest is laid out. The path onto it goes the other way: climb one of the vines on the left side of the map up to the high ledge, walk right and drop down the steps onto the mushroom island, then take its vine up to the exit. We walked that whole route with a normal jump and it works. Your report also prompted a check of every ledge across the Versal forests, and none turned up blocked.

Update, Masamune: we've added a shortcut after all. The vine hanging from the mushroom island in Western Versal Forest <4> now reaches further down. Stand at the left end of the right-hand floor, jump up-left while holding Up, and you'll catch it, then climb up to the island or on to the exit. The old route by the left-hand vines still works too. LIVE now (refresh the game to pick it up).