Hoping you don't find this post off-topic...
Sounds like a great idea searching existing Channels DVR recordings.
I maintain a small video library outside of Channels DVR that I've accumulated over the past few years.
Have about 3,600 Documentaries, Movies, One-offs, TV Shows and Specials saved outside of the Channels DVR environmet.
Using Channels DVR, I either watch&delete or save recordings outside of Channels DVR after cutting adverts.
I don't keep them in Channels DVR where I recorded them until it becomes a Media Management System Media Management
At that point I would welcome a way to search my media, but for now it wouldn't help me personally.
I understand many others have a large library of recordings in Channels DVR.