We sat with my folks in the afternoon, had coffee. Lena we left in our rooms, in the baby bed, with the sideboard up. At some point here she comes. We shat ourselves a bit, how did she manage to jump out, did she do anything dangerous. Okay, we see she's fine, but... to prevent any outbursts of angst and whatnot that the older ones may choose to perform, I simply asked her to show us how she did it.
So we went back there, and I put her in the bed, and she demonstrated. She did everything exactly right - held the upper edge with her hands while she moved first one leg over the edge, then the other and the butt, holding to the edge so she'd go legs down, then switched her grip to the vertical bars, so when she touched down she held to them and was upright. Perfect, and she was able to do it again.