Something wrong with ZDoom linedefs!

Im using Doom Builder to make a map for ZDoom, but it wont let me make slopes or anything! Ive tried typing linedef 181 for a slope, but when i test the map, it stays a flat floor. When i roll over the linedef, it says "181 - SR Lift Perpetual Lowest and Highest Floors"... anyone know wats going on???

Easy one: Your map editor is set to editing in the Doom map format, not the Hexen-based one.

do ALL ZDoom levels need to be set to Hexen format?

nope, just more features in hexen format, and its more widely used.