Yes exactly - when tsc you really want code hints for an object, but tsc can't guess its type, you can do:

    /** @type {import('../index').Engine} */
    this.engine = engine

Most of my projects have a god object at the center, so if I explicitly type that one object then I get basically all the important code hints for free.

A side benefit of this is that you can also use TypeDoc to generate docs. It's not really made for vanilla JS, but once I got over the initial road bumps I've been happy with the results.