Does a Content Management Tool/Software exist to help me quickly build video trailers from a large collection of content?
Convert all your transcriptions to subtitles (with timestamps) and save as one big plain text file, then just use ordinary search tools. This question more related to software for movies catalog.

But I think, you want not just keywords. You want "hot" places from your videos. I experimented a bit with automatic trailer creation:


https://files.catbox.moe/afoyu2.mp4
https://files.catbox.moe/hu91ip.mp4 (same, but other song)
https://files.catbox.moe/mzhc7v.mp4 (funny bug: credits as scene)


There videos was produced in full automatic way, including scene selection, beat matching and re-timing. As you can see, this is very cool, but not perfect. So, I not finished this tool.