Not a tool, but still very convenient, so it's probably useful to promote it here: The input language HDDL (Hierarchical Domain Description Language) can be used to describe HTN planning problems.
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.
HDDL parser. This parser was created to identify a wide range of possible modeling errors and to provide helpful error messages. Kindly provided by Mohammad Yousefi.