I've noticed, thanks to Aionion on the Steam forums, that Tal Kalessil does not appear in the units section of the editor. Despite owning his DLC. My guess is this is unintentional, and he was accidentally left out when DLC support was added to it.
Really? I've never tried yet, but was tempted to soon. I'll have to keep that in mind.Specifically, I believe that no "Capital" type units are visible at all in the editor, even if you make them yourself.