That didn't work either-- it unlearned the tech, but didn't remove the quickbar bonus.
However, in a completely unrelated Reddit thread I found the correct command! :D I am now back to two quickbars.
/c game.player.force.reset_technology_effects()
(This command recalculates your bonuses based on your current techs. Note that this should correct the bonus for options in your mod like "Mining Productivity Bonus.")
Thank you for the time and effort in helping me. I am enjoying the mod and the options it affords.