Protocol handler extension for WebDAV

I created an addon to see a webdav share right from a browser

Now I wish to make it handle all links with protocol dav:// davs:// and webdav:// webdavs://
I have to capture all four of them because the dav protocol schema looks like not specified and different tools use different schema e.g. LibreOffice webdav:// but GNOME nautilus dav://

I found that for PWA is should be somewhat possible

But the dav schema is not listed in permitted. Can it be supported by a browser in future?

Also I didn’t get when and why the ext+something schema may be used. Is it intended for extensions/addons?

I tried to use the web+dav schema in the manifest.json but I didn’t worked. Chrome reported the protocol handler as error in manifest.
Probably it should be used only for PWA but it looks like the feature is curently just a proposal
I didn’t read the thread yet but anyway I need to handle the dav links.

Chrome article