Filtering Annotations by ID

My goal is to load annotations and filter them by their ids so they are easy to locate. I was able to follow along [here](https://github.com/google/neuroglancer/issues/227#issuecomment-651316216) to load annotations. In your comment, you state that additional files are required to filter by annotation ids. I was wondering what these additional files are and where they need to be placed.

I have tried adding [single annotation encoding](https://github.com/google/neuroglancer/issues/227#issuecomment-651316216) files in either the directory specified by the `by_id` `key` or the `spatial` `key`. However, neither seems to have an effect.

Any help you can provide would be great, thanks!