As far as I can tell from the source code, in GT 5.09.xx steeleaf requires a block with ore dictionary entry "oreSteeleaf" or "blockSteeleaf", but I'm not sure such blocks exist even with Twilight Forest installed - I don't have it installed myself, but http://ftb.gamepedia.com/Steeleaf indicates that Twilight Forest only provides steeleaf in item form as chest loot, and I don't find any such blocks defined by GregTech.
Thx for answer.