TLA+ Toolbox: The fully featured (if somewhat outdated) IDE for TLA+. Includes modeling, document generation, and live syntax checking.
VSCode TLA+: Lighter weight IDE with textfile based model configuration. Generally more responsive. The latest alpha version, found here, has a debugger that might be useful to you while getting a handle on the language.
Tools for TLA+ display
tla2json: Used to turn trace output from toolbox into json for automatic trace widget generation.
LaTex: Used to render the LaTex output of TLA+ to dvi format.
dvisvgm: Used to convert the dvi formatted TLA+ specifications into SVGs that could be displayed inline in the website.