Is putting the actual quotes into the metadata a reasonable approach to building a database of quotes?

You can change the checkbox to look like something different, for example, the quotation symbol holroy showed in his examples (which is what I did with mine). Here’s a post that talks about how to do that, and of course the important parts are thanks to holroy:
Alternative Checkboxes (Icon Bullets) - Copy and paste - Share & showcase - Obsidian Forum