A mechanic is found in the editor on the tab
General->Mechanics.
A mechanic is a Thing that is always live on the hero/character. So create a new one and give it a unique id of
mechFCB. Then bootstrap your new FCB's to this mechanic and save your changes.
But you can't use Test Now! with a mechanic. Go back to the normal HL window and press
CTRL-R to reload the game system.
Now sense the mechanic is always live anything bootstrapped to it will also be live. As an FCB is tagged to a specific race/class combo the FCB will only show when that race/class combo is added to a character.