If we compress that desktop-scr folders to ZIPs and index it, it might be compact system.
Just testing one topic 'Controls':
Completed Controls.chm file is 4,525 Megs (includes TOC and Index)
ZIP all .md files under 'Controls' is 4,356 Megs (including a TOC.yml but no F1 Keyword file)
So not much size difference at this point between raw .md and final .chm.
Normal .mshc is ALSO in XHTML format (like .chm). The .mshc TOC looks similar to .chm HHC TOC and the F1 Keyword section looks similar to the HHK so I guess that after adding these to the file list the .mshc file size will be comparable to the .chm as well. I may try to make a complete Controls.mshc just to see.
Using .md files directly would save a lot of work obviously not needing to convert to any HTML, just build some sort of new TOC and search index. If the new viewer could use the TOC.yml then - well nothing needs to be done except download and zip it.
The new viewer would need to support a number of things available in the compiled help file formats (links, Pictures, tables, lists, etc). The .md files themselves still do need a lot of work however.
John Z
Update: Well I used mshcMigrate utility from HelpWareGroup to migrate the Controls.chm to .mshc and .cab file formats.
Controls.cab is 9,553 Megs
Controls.mshc is 10,859 Megs
Unfortunately I can test the conversion as I don't have MS Help 2.x runtime. However even if fully functional the size is not favorable.
Conversion results:
Time to complete: 5 mins, 38.41 secs
** Errors: 5, [ ] Warnings: 8,343
HTML files requiring attention: 2
Update again: Using TimoVJL's TLWHViewRE-2018-11-16_bin.ZIP file attached above I'm able to read the Controls.mshc I created. Need more time to assess the successfulness of the conversion - but it is usable!