Fast place aka auto clicker for blocks, applies to other things as well such as snowballs, enderpearls, fishing rods etc.
Some things such a snowballs it's okay but you wouldn't want to accidentally throw 2 pearls cause of this, so I suggest also adding a white- or blacklist to fastplace to...
No matter the settings scaffold sometimes just shifts even if not near the end of a block or holding non whitelisted items just keeps u shifted and u can't unshift until u toggle it off and press shift once.