The profit switcher will automatically do Dual mining if it's more profitable. Please note that Dual Hashrate value for Ethereum and the secondary coins (Decred, Lbry, ...) will be used in these calculations.

When you have a Managed Profit Miner running, you can right click on it and select View Details. In that dialog you will see more information about profitability for each pool and combinations of Ethereum and secondary coins. This gives an understanding of how the profit decisions are made.