Safari on Mac: Chrome bookmarks lose folder structure

No problem. Bookmarks are stored in a plain text HTML file which preserves their organizational structure. To edit HTML files (or any text files for that matter) I use BBEdit but you can use whatever plain text editor you see fit. Other than that the Apple Support document Sort, alphabetize, or rearrange bookmarks in Safari on Mac - Apple Support explains how to organize them, under Rearrange bookmarks. That may be more or less convenient than editing them with a text editor, so you'll have to decide.

‎BBEdit App - App Store

Another potentially more convenient solution might be to import those bookmarks into Brave:

https://support.brave.app/hc/en-us/articles/360019782291-How-do-I-import-or-export-browsing-data

I can't help with Google products but Brave is essentially Chrome without the Google baggage. If they import into Brave while preserving the folder structure perhaps they will export / import into Safari the same way. I don't know so try it.

https://brave.com/

... Then when I went to move them to a folder I created in the Safari tree the structure they were in on Chrome in Windows showed up. How do I get the MAC to show the structure I had them in in Chrome?

I'm a bit confused by that question, but organizing bookmarks is explained here: Sort, alphabetize, or rearrange bookmarks in Safari on Mac - Apple Support