The OP’s plugin is a SourceCodeAcessor, it only allows for opening files by clicking at them inside of Unreal Editor, but nothing else - it won’t provide code competition, LSP navigation or syntax highlight, it does NOT serve any other purpose than opening files. Do you actually need this functionality?
Also, you don’t need to apply those patches into Engine source tree. You can find a standalone plugin on OP’s github (link below), but have in mind that code is unlicensed and abandoned.