AFAIK the configure wrapper should already provide autocomplete powered by TypeScript also to JS projects.
You're right to the fact that currently JS users won't get it out of the box, but we can enable it.
Can you check if using configure wrapper actually enable autocomplete in your JS projects?

I can, but I'll need to update some projects to v2.0 version to check that. I came back to maintain some things after long time, so my setup is kinda outdated.

You mean @quasar/app v2? If I remember correctly, those wrappers are there since v1.x 🤔

You can see this by looking at q/app v1 branch here, where they are already used:

Oh, right. I tried it now, it doesn't work with them - idea doesn't pick up their typings, so they are just treated as just blank functions. Only the doc comment seems to work in this case.

I'm searching stuff on this topic. Adding JSDocs on quasar.conf file isn't a good idea as we also have these kind of TS-powered typings on boot files etc. It's a thing which must be fixed in the monorepo.
Best idea would be to add those JSDocs into ui/wrappers/index.js implementation, but I could not find an explanation anywhere about how does IDEA crawl for types.

Eg, would this work without any import from @quasar/app when actually used?

/**
 * @param {ConfigureCallback} callback
 * @return {ConfigureCallback}
 */
module.exports.configure = function (callback) {
  return callback
}

Can you try it out in some way?

@panstromek any news?

Sorry, I haven't had time to look at this more.