In redundancy mode, there is only one group "Redundant Profibus" on the General tab where you can set the slave numbers. There is no entry any more for selecting the bus number, as the active slave in redundancy mode is always generated on both buses simultaneously.

Each of the two S7-400H CPUs sends data to the slave on its own PROFIBUS system. This is why an active slave always has to be available on both PROFIBUS systems.