Don't forget that the tools listed here are just the ones that don't fit into any of the other categories that are available (such as planning systems, plan verification, etc.) Further, if there's some tool/software that you think should be listed, please reach out!
VSCode Extension (called HDDL Parser) is an extension of the famous VSCode development GUI that provides syntax highlighting and useful real-time validations, such as type checking, undefined constants, etc. Find it on the Extension Marketplace. Developed by Mohammad Yousefi.
HDDL parser. This parser was created to identify a wide range of possible modeling errors and to provide helpful error messages. It further provides useful capabilities for interfacing with planning software, such as a JSON export of the parsed HDDL files. It is actually the tool used internally by the above-mentioned VSCode extension. Thus, also provided by Mohammad Yousefi.
LaTeX listings syntax highlighting for HDDL, JSHOP's input language, and PDDL. Created by Mauricio Cecilio Magnaguagno. Find it on git
Tool for drawing HTN solutions given the required output format of the IPC 2020. Also kindly provided by Mauricio Cecilio Magnaguagno.