Odd, but I click on the house ruled icon and even go into the campaign settings without finding the "show illegal feats" tab. Has there been an update to the builder since it went live? Mine has always said that it is up to date.
Go into "Build" and then "Feats." Click on the house rules icon in the upper right corner of the table, then select "show illegal elements."
It takes a while to find this stuff, when there isn't really a manual.