missing Find symbol/engines/"output web apps" list

In the case of a user starting to type in their omnibox, and wanting to "complete an action", such as ex:
- would like to convert a/this file in an other fomat
- would like to CRUDSearch information somewhere,
- generally accessing a web app, and maybe getting a "url pipeable output"
- etc.

some pattern of missing engines, symbols and semantics emerge, can try to list them until we find an app that provides the desired functionalities.

Maybe can also be discussed on:
- https://github.com/internet4000/find/discussions/
- https://matrix.to/#/%23i4k-find%3Amatrix.org

No files, tests, or implementation entry points are named. Start by reviewing how the browser omnibox handles symbols, engines, and URL-pipeable output, then use the linked GitHub Discussions and Matrix room to narrow the proposal. Done should mean an agreed scope and concrete list of missing functionality.

Written by the indexing model from the issue text.