Sorry for the late reply. Since you have a gmail address as do I, the simplest way is just to email the AppImage file directly to only me: phylsmith2017@gmail.com --- what happens when there is a big file is that gmail will automatically upload the file to a specific spot and provide a link for me to download. Not sure if you want to add the Help Manual documentation first as explained below.

So I need to know from where and how to copy these html files?

https://cinelerra-gg.org/download/images/HTML_Manual-20241031.tgz

Just download the tgz file and tar xvf to wherever you have bin/doc so it can be copied to AppDir/usr in bld_appimage.sh.

Can the bld_appimage.sh take the wanted file name as argument, or is it just fine to rename it afterwards?

It is just fine to name it afterwards; that is what I do when renaming for the website to include the date.

opening index.html and "cinelerra.html" is "Secrets of Cinelerra", Version 4.1 by Adam Williams

We always want to have these files with the source to recognize Cinelerra's origin and continuance.

And not to forget: it is thanks to Andrew's patchwork and time consuming guiding that has made this possible !

Yes, that goes without saying, but I should have said it anyway.