### Steps to extract the indices from `octave's official documentation` to add them to `qhp` under `keywords`
Copy the `HTML` files named `Concept-Index.html`, `Function-Index.html` and `Operator-Index.html` from `octave-5.2.0/doc/interpreter/octave.html/` to here. Then run the python scripts named `concept_index_parser.py`, `function_index_parser.py` and `operator_index_parser.py` one by one using `python <script-name>`. On running these scripts, an output file named `output.txt` would be generated. It would be containing all the indices. Simply copy the file contents and paste under the `<keywords>` section inside `qhp` file.
Simply get the QtHelp files from the official Octave repository. Get the files from `octave-5.2.0/doc/interpreter/`. The files are having `.qch` and `.qhc` extention. You could also run the perl script named `mk-qthelp.pl` and pass in the arguments as `octave.html` and `help`. ie `mk-qthelp.pl octave.html help`. After runnning this script, the help files are generated.