The default web app has a feature for this. When you’re writing a post, as you type the title, it automatically does some sort of search in the community you’re posting to for the title you’ve entered. So if you write “avatar” as the first word in the title field, it will search the community for posts with “avatar” in the title. Don’t know how many other apps or front ends do the same, but it is actually a helpful feature for exactly this.