Where are clipart stored on filesystem ?

I would like to enhance some cliparts, but do not know where they are stored on filesystem. The one you get by Insert/Media/Gallery.

Update

Thanks to Opaque that helped me find a track, I found the location of the Gallery folder in Tools -> Options -> LibreOffice -> Paths -> Gallery which is ~/.config/libreoffice/4/user/gallery/. This folder contains 2 files:

2.0K Sep 25  2017 sg30.sdv
565 Sep 25  2017 sg30.thm

2K seems a little small to contain a bunch of cliparts. file report it as a Composite Document File V2 Document, Cannot read section info. How do I read it ?.

The system-wide clipart in linux is stored in /opt/libreoffice6.4/share/gallery. The files you found apear to contain references to graphics and sounds that have actually been used. If anyone knows anything about the structure of them, I’d like to know.

Under Windows 10, the files in corresponding subfolders are in my directory
C:\Program Files\LibreOffice\share\gallery

Addition: And %appdata%\Roaming\LibreOffice\4\user\gallery (or what else you may have defined in Tools -> Options -> LibreOffice - > Paths for type Gallery) if you define your own “Themes”

Thanks, but I found them in the repos (gallery\source\extras - libreoffice/core - main, development code repository). I had to clone the repos anyway to publish my change.