It seems that the consist editor does not see the locomotive type (steam, diesel, electric) if the loco uses include files.
So for example I want to use a steam loco DR_BR_4MT_76005-D03 and I select "Steam" then the loco is not on the list:
I can find the loco if I choose ALL rather than steam and search for the loco:
I thought this may happen because Type ( Steam ) is in an include file, the main file looks like this:
So I tried adding Type ( Steam ) to the engine section:
...or even at the top of the wagon section:
but none of these was able to make the loco show up as a Steam loco in the consist editor.