there are actually 2 editors: one official, and the other not.
the official one is called keytool (ktool). its pretty weird and all, but thats what watson used for puzzle designing. you, uhh... have to... write code in other to set options for keys and doors (which is highly exploitable, so you can make a player spawner and stuff like that). and you cant undo, and stuff. but its made on the official engine.
the fan-made one is called... i wanna lockpick editor... made by l4vo5, which is somewhat better, but since it only started development, its in beta and somewhat glitchy. its made on its own engine (not even an iwbtg preset one)
and its not as glitchable as keytool (no custom code, 0x0 doors, off-grids, confusing key counts, etc.)
if you need some kind of help, or just a place to talk with iwl fans, you can join the unofficial iwl server! its pretty active, and even lawatson himself was there! he left, sadly...