copy one of the section in es_systems.cfg to use for kodi. You’ll need .sh .SH for the extensions.
Create a kodi rom folder, then inside that folder you could copy the kodi launch script from where it’s at now to the new kodi rom folder. I think the script is currently sitting in the ports rom folder.
From there kodi will show up, but you might need a theme. you can simply copy one of the theme folders for another system and modify it, but I think most themes now may come with a kodi theme already.
^^ my other hobby