I accidentally placed the wrong workbench and i want to get rid of it but i can't figure out how.

wish i could be more helpful, but from what I can tell as of yet, you are unable to pick them back up, unlike tools that the recycler can process  

Press E to enter Edit Mode; then press Del (fn-backspace on Mac); your pointer should change into a wastebin, which means when you select a structure (like a workbench) it's deleted. We know this isn't ideal but it's still early days, so a more elegant solution isn't implemented yet :)