ahoneymac wrote: So the idea would be to have, say, 10 libraries for my various categories and projects, and open each one up at a time?
No, but that may depend on what you mean by categories. I separated my wife's family from my family into two different Libraries, because when I was trying to work out relationships of people who died before we were born, I'd try to fit cousin John into my family and then suddenly remember he was one of hers. I just gave up and separated them-- which only works until we're married, and then the families mix. Work is separate from home, but there's lots of mixing. Because of this mixing my "main" Library, the one that is shared through iCloud Photos, is the Favorites of them all, with cool old family pictures, photos of work colleagues at my daughter's wedding, etc-- but only the best ones.
I have a Nikon Library, because I'll go to an event, take 1000 pictures, but they all look sort of alike-- there might be 40 pictures from the bunch that I really want to look at or show others. So I copy those to the Favorites Library once I've figured out which ones they are. But I keep them all in that Nikon Library-- you never know when you'll change your mind.
The "categories," like flowers, horses, birds, Christmas, vacations, and so on, are not Libraries-- they're albums in folders.
In the Library view of any Library, all the pictures in that Library are together, no separations, and they are organized by date. You can choose by date addded to Photos or by date captured by the camera. The Years, Months, Days thing just refers to that Library view. This is provided by Apple for our entertainment— it’s not really an organization technique. I almost never use the Years, Months, Days thing, though I use the full Library view as I need.
The most obvious way yo organize pictures is by date taken. So I have my pictures in albums representing events with a date, like "25 09 20 Balloon Festival "or "25 09 05 TexRose Sport Cup" or "24 11 16 Horse Jumping Tyler," and so on. These a"events" are Albums. They are kept in Folders of albums. Starting with dates like that, year first, allows me to put them in alphabetical order that is also chronological
Depending on how mayn pictures I’m taking, I might have folders named for months, like “25 09” or “25 07-08” etc. Those might go in a 2025 folder. Then I put year folders into decade folders, like I have a 2010s folder for all the year folders in that decade. But this is only one level of Organization.
Two of those “events” were both horse shows, so I put those albums together in another folder called Horse Shows. Each of those pictures, then, is in two different albums in different folders. I’ve taken other pictures at other Balloon festivals, so I have a folder for those. My wife has taken lots of flower pictures, and I have, too, so they go all together in a Flowers album. They are also in event albums in date folders.
Photos provides albums for people and pets, so all the pictures of my wife are more or less automatically put into those albums. More or less automatically, because Photos doesn't recognize backs of heads, for instance.
I have albums of Astronomy pictures, Infra-red pictures, birthdays, holidays, or other groupings. I have a folder for “Wife’s Family” and one for “Richard’s Family.” All of these pictures are also in albums of events by date, as well.
But the best thing for organization is keywords. I give every balloon picture the keyword Balloon. Then if I’m trying to find a picture of my nephew with a balloon but without his mom, I can narrow down the hunt using a Smart Album, asking for keywords of Brian and Balloon and not Ann . Keywords and Smart Albums are the great power of Photos!
To help with figuring out which picture go in Favorites, I rate the pictures with stars. I use keywords to do this, as here:
Choosing Favorites using Keywords in Mac … - Apple Community
Photos will help with some of the organization, but it's really up to us to had keywords, captions, titles, and choose what albums and folders works for us.
