The dive planner in Suunto EON Core and Suunto EON Steel is for no decompression dives only and uses one gas. You can change depth and oxygen percentage for the planned dive, and the dive planner will show estimated no decompression time and gas time accordingly. Remember to set tank pressure, tank size and consumption rate to properly estimate time calcuations.
See more in the EON Core and EON Steel user guides in section: Dive planner
We recommend using Suunto DM5, you can plan complex decompression dives with multiple gases.