I found my foot-shaped darning egg and am, as predicted, full of glee. I’ve included a photo of it inside a sock heel with my hand gripping it, so you can see the idea. This sock doesn’t need darning, but if it did, the wooden form inside it would help support the sock and also keep me from accidentally sewing through two layers while darning.
Edit to add some more alt text I’d meant to put in before.