I just submitted feedback to Apple because I was shocked that there was no apparent way to add a folder bookmark to the Home Screen. You can save a website to the Home Screen on iOS and created an alias on MacOS. So, I don't think this is something that's technically not possible to do nor a foreign concept for Apple.
Use case: I'm traveling and have all my documents in a folder in iCloud. Yes, you can set that folder as a favorite in Files but it would be more convenient, given. the hectic and stressful nature of traveling, to simply have access to that folder from the Home Screen.
Even better, now that I think about it, it would be great to have a Smart Folder so any document or email or booking confirmation or SMS or WhatsApp message, etc., that I tag in iCloud with "London" could easily be found from one spot on the Home Screen. Perhaps there's a future where we can ask Siri to show me all my documents and messages for my upcoming trip (not that I trust AI will ever be smart enough to figure this all out).
Tested some more and unfortunately it doesn’t look like you can choose a Tag in step one, however you can select multiple folders and you’ll be presented with a pick list.