Editing Workshop Items
Editing a file is exactly the same API as creating one.. you just need to get an editor for it.
var result = await new Ugc.Editor( fileid )
.WithTitle( "My New Title" )
.WithChangeLog( "Changed Title" )
.SubmitAsync();
You only have to change the parts you want to change, and can even include a changelog.
Garry's Mod
Rust
Steamworks
Wiki Help
S&box