I was able to get highlighting by manually setting the project file. Nice, yah I looked at the VSCode Nim based extension. Its confusing with all the vscode/nodejs file apis, but fundamentally it just calls some form of execProc to start nimsuggest. Impressive that @saem got it running with Nim bindings.
If nimsuggest just finds the default nimble file, then it'd be possible to modify the vscode extension to try that, and failing that to start a per file instance. Though nimsuggest would probably need to be able to print if it found a project nimble or something? I'll toy with it. I was hoping the nim-lsp would do that, but it wants some json config. I prefer it to do the "sane thing" first then let me customize it if needed.