[Mobhack]

The "show unit ids" on the gameoptions screen reports the Mobhack Ids on the various purchase screens, so you can ID a specific unit or formation ID number, e;g for an error report.
(Game Guide, Running WinSPMBT, Game Options Tab 2 (Misc) section, description paragraph in "Show ID Numbers".

That has nothing to do with the Formation IDs superimposed on the troops on the map in the full game. These are on by default since most users wanted it to operate that way. Use the 5 key to toggle on and off.
(Game Guide, CD Extended features, "Show/Hide Formations IDs" section).

Andy