max amperage of WAGO 222-415 connector?
It seems you're hoping that the capacity is a function of power, so that by decreasing the voltage you can increase the current.  Unfortunately, that's not the case.

Voltage maximums for connectors are generally a function of the insulating characteristics of the materials.  If you exceed 600V for this connector, you may get arcing or the insulation may break down.  

Current maximums are due to the resistance of the connector and wire used for insertion.  These connectors don't give a resistance rating, but 20A will generate a lot of heat in the 28AWG wire these things are rated for, and you could exceed the maximum temperature of \$85^{o}\mbox{ }C\$.  This power dissipation is not due to the voltage present on the wires, but the voltage across the resistance inherent in the connections, so it doesn't matter whether you're using 600V or 12V. 

Also, unless it says otherwise, these are generally static ratings: You need to plug everything in before you turn the power on, and turn the power off before you unplug anything.