Is there a way to mark or add photo to a collection for later deletion in macOS?

PommeDuCanada wrote: … but not required

The thing is, we're just users like you. We are not required to even read your post. Many of us just hang around here in case we can be helpful. I'm sorry I missed the "macOS"-- that information is usually put in the signature section in response to the questions that are asked when posting.

Looking at the filter in the top right, I see some fixed options to filter by, and "Keyword Manager". I see it provides a set of tags to filter by, but it isn't clear how I could leverage this for my request.

As MrHoffman briefly suggested, tagging is done with keywords, and one method to take advantage of that Filter is to use those keywords. See this:

Find photos by keyword in Photos on Mac - Apple Support

You can also see this:

Choosing Favorites using Keywords in Mac … - Apple Community

which talks about using keywords and Smart Albums for a particular purpose, particularly the way I "tag a photo for review."

Actually, the Filter that I was talking about is in the View menu when using Library>All Photos:

This is similar to the Filter in the Library view in iOS 18.

The best feature of Photos on a Mac is the Smart Album. You can ask for all the "river" keywords that are in the "Grand Canyon" album which are not Favorites, and so on. We might use Smart Albums for everything instead of regular albums, but Smart Albums don't show up in iOS.

Mac Photos is way more versatile than iOS. There's lots of subtleties in Photos, and there's lots of experience available here, so let us know what puzzles you.

PommeDuCanada wrote: … you mentioned it didn't work on iOS. …I'd like to be able to browse and "mark photos" for a later action while I'm out and about.

Most of us with Macs don't use our iPads for much organizing, because it's harder. The one way to "tag" a picture on a mobile device is to use the "favorite" tag. It's fast, it's simple, and it's visible in all devices. The downside is that "favorite" is usually used to mean, well, favorite. So if you decide to mark your best pictures with a keyword, instead, then you can Filter by Favorites in even in iOS and iPadOS.

iOS and iPadOS don't let you see keywords, but you can search using keywords. Unfortunately, if you search for "horse" you'll get all the pictures with the keyword "horse," but you also get every picture with anything that looks like a horse (to a computer.)

You can, of course, just select a picture and "Add to Album" to pass the pictures around. You can do this with the "Not in Album" Filter turned on, and add pictures to this album or that one pretty quickly. I'm not sure I see anything wrong with that. If you haven't seen the "Not in Album" filter on the iPad,

Another way to separate pictures is to use a Shared Library, shared with yourself. You transfer pictures from the main Library to the Shared one, and back. I don't use a Shared Library, but I think it might not be the best way to "tag" pictures.

Keywords are included in Exif metadata. You use the Keyword manager to edit and delete them. You can add keywords in the Info Window for a picture or group of pictures.

Are you talking about a Mac, an iPhone, an iPad, or what? What OS are you running. We can't see what you're doing.

"Bonus points" is pretty condescending and not really appropriate here.

Collections like Trips and Memories are provided as a little gift from Apple, and they can't be modified.

The Library view shows all the pictures in the Library. You can use the Filter to see only certain members of the Library, like only those not in albums.

Let us know what device and OS you're using, and we might be able to help with the "tags" question,

PommeDuCanada wrote: Okay, I mean that makes sense that portable devices are mostly for consuming photos...I may need to rethink my strategy.

Obviously a Mac can do a whole lot more. But iPads are certainly getting closer. And, as you say, an iPad is a perfect device to view and share pictures.

PommeDuCanada wrote:

Where did it populate the existing keywords from? I can't consistently see whether they are from content analysis or many of my descriptive file names prior to uploading.

Many websites will add keywords to photos to identify them. Also if you received photos from other Mac users they may have added them. Normally you have to add them via the Command+k keystroke to bring up the Keyword editing pane.

Use a keyword.

PommeDuCanada wrote:

Where did it populate the existing keywords from?

Probably from the exif. (q.v. exiftool)