I'm considering using Lightroom over LrC, *but* ...

I have a 10,000 image library currently managed by Lightroom Classic.

The images are hierarchically ordered by year/month/day and cross indexed by

keywords and collections. To manage this with the current and future

version of Lightroom, I need to be able to look at collections of the images

by keyword or collection, and that means looking and photos that come from

multiple directories and not all of the photos in each of those directories.

It's not obvious how to do that.