The Combo tab allows you to manually input two legged spreads and other two legged options strategies not specifically supported in any of the other Options strategies.
Note that because Schwab currently only accepts two legged orders, if you complete a stock leg (Leg 1), you will not be able to complete Leg 3, and vice versa. Also, the StreetSmart Edge™ Combination order is not the same as the Combo strategy on Schwab.com.