What do the special options in the Census menu do?

They have no effect as of now, and were in fact explicitly called out in the full changelog as a work in progress when introduced.

This feature has been implemented for a while now, though a slightly less complex version of it. There are no longer Senators, only a single position called Leader that you can assign.

Any kitten can also have one "trait", which doesn't need to be related to their profession. Each trait grants a bonus to some aspect of the game. The bonus applies for whichever trait your Leader has.

The list of traits can be seen in the source code for the game, but as of right now (v1.2.0.0) the traits do the following things:

• Manager - boost to hunting (huntRatio += 0.5)
• Scientist - discount on science needed for buildings (cost *= 0.99)
• Engineer - boost to crafting (craftRatio += 0.05 )
• Merchant - boost to trading (tradeRatio += 0.03 )
• Philosopher - discount on religious upgrades (cost *= 0.99)

The other two (metallurgist and chemist) don't do anything yet.

In addition, the kitten assigned as Leader will get a bonus to whatever job they are doing based on their rank (I don't believe rank has any impact on kittens other than the leader.)