Following an earlier thread where I was searching for an application to document my PBLs in a HTML website, by extracting comments etc. from my code, I ended up writing something, which I have attached, and offer for free for anyone's use.
It can document a single PBL, or all of the PBLs in a target (PBT).
It's not a completely standalone solution, as it requires the installation and use of the generic documentation generator NaturalDocs (www.naturaldocs.org).
What's in the Zip file is a PB 2021 workspace, target and PBL with my application in it, configuration files for NaturalDocs, and a fairly comprehensive Help file explaining the required setup and usage.
The generated documentation can be improved by writing your comments at the start of functions, events etc. in the style it expects, and for objects that don't contain code, supplying a Comment in the object's Properties. It's all explained in the Help.
I'm sure this doesn't do anywhere near as good a job as VisualExpert (https://www.visual-expert.com/) but it's free! It was good enough for my purposes, which was helping a new PB hire to understand the common library used in our applications.