I need to continue to manage my photos in folders and sub folders on my mac. So I need to able to isolate new photos to add to my files. And I still want to be able to upload selected picture folders to my other devices for viewing purposes.

Roy's iPad wrote:

... I have all my photos in folders and subfolders on my mac. It represents years of work that will be lost. The subfolders will be deleted and all my photos jammed into to top level folders. That's an impossible situation and several thousand photos become impossible to find.

....

That is not necessarily so. When you import photos into Photos on your Mac from nested folders, you can select "keep folder organisation" when importing, and the folders and subfolders will be recreated as folders and albums in Photos. have you tried that? See: Import photos from storage devices and DVDs using Photos on Mac - Apple Support

* If you selected a folder of items that contains other folders organized in a way you want to maintain, select the Keep Folder Organization checkbox, then click Import All New Photos.

You should be able to see all folders and albums when browsing your library in Photos. The only problem is that not all applications are currently able to see the folders and albums when using the photo picker or media browser to access your Photos Library from other apps. For the time being I am no longer even tryig to access my Photos Library from other apps. I prefer to select the photos in Photos, where I can see my albums and then share the photos from Photos.

There are other apps if Photos doesn't do what you want. Check out Mylio, for instance.

Why don't you test it for yourself. Create a new library with Photos and import the greatest set of subfolders you have into it. See if it can handle that many subfolders. If it doesn't do what you want must delete the library. No harm no foul.

Photos on my Macs, iPhone, and iPad are having no trouble seeing my hierarchy of folders and albums in iCloud Photos. I know that some other programs on the Macs are having trouble seeing the hierarchy. Is that what you are discussing?

Roy's iPad wrote:

... From there what is the process for accessing my file photos for other uses such as family tree or attaching to an email etc.? Thank you for your interest in assisting me in this matter.

Roy

That will depend on your system version.

Starting with macOS 13 Ventura, we can no longer see the folders and albums in our Photos Library, when we access it from other applications that do not support Photos fully - we can see the the the structure of the Photos Library when accessing it from Mail, Pages, Keynote, but not from Safari or other web browsers. That is independent of the use of iCloud Photos or not. we are seeing the folder structure of the photos library and the albums when working inside Photos and in some selected apps, but not when uploading to facebook or similar. Then we will just be seeing an endless list of photos without structure.

Photos can maintain a folder hierarchy and keep it during import as shown here:

Once in a Photos library photos can be gourd further without disturbing the original hierarchy, i.e. a photo can be in multiple albums because they use pointers to the original so they don't take up additional space on the drive. It's a databased system rather than file based.

Personally, I use both systems. The file based system is one of my backups and the library is the working system.

In a Photos library will search for faces and group them together is smart albums. So if you're looking for all photos of one person it's easy to accomplish.