OK. I'll try to explain it....
Return Of the Triad (and some help tutorial from El Zee's site), allow you to make custom maps for that TC; in the same way that ROTTMD make them for ROTT. In other words, you can make custom maps using same stuff than the TC, that's: ROTT stuff, previously converted by El Zee into Doom format.
I have (supposedly) all tiles and characters in the File included with the TC (I can't remember which one of the 2 it's this one, but it's one of them). All I need is to use a Doom Editor, and use this ROTT stuff, already made, to build my own maps. Doombuilder lets you do it, but in El Zee's words, he also used Slade 3 to develop the TC; so that's the reason I asked if Slade 3 will let me make my custom maps with stuff provided by the TC.
I can use Doombuilder, but I need to install dotnetfx3setup to use it; and in case I can't, I would not be able to use Doombuilder; and as Slade seems to work without any update, I asked if I can use it instead.
I know I cannot build Doom maps (I mean, Doom characters, tiles, etc), but what I want is to built maps for the TC using that provided ROTT stuff.
Have you understood now?
Thanks for answering and help, and see you soon, mate.