I have a 'homebrew' user guide for XLD. I checked there and in the app and didn't see a way to add data to the database. It's not up to date but has recommended settings for ripping (some of the recommendations may be different than the defaults). I'll email you the pdf if you pm me with your email.
I had a fairly big collection of CD rips accumulated over the years and needed to to some metadata housecleaning. Best option I found for this is Metadatics which is $10 IIRC in the Mac App Store. Info for many discs, especially more obscure ones, in the databases is often inaccurate, incomplete, or missing (or some combination) and Metadatics makes fixing these problems fairly easy and quick.
I do use Tidal hi fi but have ripped a lot of my CDs (losslessly) over the years so I also needed a solution for local content and these two apps cover the bases well for me.