They screw into my desk and act as posts, but I’m missing one of four to hold up a plank of wood, and I dont know what they’re called. I called them dowels in the accessibility image, but I dont knownif that’s correct.
Any help is appreciated.

Another image of the thing individually.
They are also know as shoulder screws… https://www.mcmaster.com/products/shoulder-pins/shoulder-screws-3~/
They go by a few names, depending on use. I would call them standoffs if the end has threaded hole in it that the thing they are holding can screw into, shelf supports if they go sideways into something to hold a shelf, or semi-threaded dowels as a generic term.
I think shelf support is my answer! They screw into a side of my cupboard, where it holds up a plank to make a shelf! Thank you!
Standoffs is what I know them as
EDIT: No idea where you are located, but here’s an Aus store with some standoff screws. Hope that helps
EDITEDIT: The link lol - https://littlebirdelectronics.com.au/collections/standoffs-screws
I was thinking a peg but the other answers are probably more accurate



