How to Delete Apple Photos images from a Library (on an external drive)?

A big

on not using a "referenced" library.

baldoyler: If you open the library without the referenced originals mounted or relocate the referenced originals the link between them is lost and must be relinked one by one. Without the link there can be no edits or projects created.

And no, there's no way to automatically delete the reference original file if the photo is deleted from the library. In selecting "referenced" you're electing to managing the files yourself. The now defunct Apple Aperture was designed to handle referenced files but it was a pay for app.

If you want an app that' powerful and designed to use referenced originals took at Adobe Lightroom Classic, Capture One, digiKam, Mylio Photos, and Adobe Bridge.

I'm not sure what you mean by 'recommended' or what the recommendation is based on.

Recommended by experienced users, and the recommendation is based on two things: One: posts like yours, made by people who don't realise the implication of the decision you made, and two: working with the application and realising that it has none of the tools necessary for managing images stored without the library package. Rule of thumb: If you want to use a referenced library don't use Photos. Or put another way, if you want to use Photos don't use a referenced library.

But clearly Photos allows users to have a 'referenced' Library on an external drive (SSD, in my case).

They do, but I've yet to see a convincing usage case for one.

I absolutely do not wish to have Apple or anyone else pointlessly storing TBs of photos on iCloud (at cost of money and energy) just so I can move them between a Mac and a MacBook Pro, as I can with an external drive.

Sure, but did you consider just turning off the iCloud Library? Or not using the Library as the System Library?

Is there not a simple key command to delete referenced photos from inside Photos, as can be done for managed photos?

No. Nor a complex one, nor any kind of one.

Apple has an excellent piece of software in Photos, but so many of the basic functions seem unfinished or 'hobbled' in some way.

It's a give-away app, and you get what you pay for.

I'm not sure I understand -- are you using a Referenced Library rather than a Managed Library? A Managed Library is one in which the original picture files are imported into the Photos Library with this setting:

This is the default setting, a Managed Library.

A Referenced Library is not recommended.

If I wish to share the library between two Macs (an essential to a working life on the move), I either have to use a referenced (as opposed to managed) library, or I need to pay for iCloud storage.

You're really quite confused about Photos and its capabilities. This is not necessary at all. Simply store the managed library on an appropriately formatted external and, as long as you have the same version of Photos on both machines, it's just a matter of plugging it in and double clicking on the Library.

But Apple have essentially removed a feature in order to charge (through internal storage or iCloud storage or both).

Nope. That was never a feature of Photos nor of its direct antecedent iPhoto. Just never had that capability. Aperture did, and cost as much as Lightroom. As for Adobe's subscription model I will say this: piracy of LR and Photoshop is virtually non existent and I have permanently up to date versions of both for a fraction of what either one would have cost me per annum prior to this. And you know, even if I stopped paying the subscription tomorrow all I would lose is the map feature and the detailed image processing features. I could keep using the app as my photo manager.

If I would comment on anything it's that you have a tendency to assume a lot but not actually know very much. You assume that Photos has tools it hasn't, you assume that you have to use the iCloud Library with a managed library, and you don't. You assume that a referenced library is necessary to share a library without iCloud and it isn't. So I'd bear that in mind before you editorialise more.

baldoyler wrote: …cuts down on costs of iCloud etc

There is no connection between Referenced, Managed, and iCloud. As I said earlier, a Managed Library works perfectly well on an external drive and without iCloud.

…not sharing all my thousands of photos with anyone or storing them on anyone's servers.

Again-- no connection.

Richard.Taylor wrote:

Or you just unplug the drive from one computer and plug it in to the other. Double click on the Library. No iCloud involved.

Remember both computers must be running the same system and Photos version.

All the way back in Lightroom Classic 6 this was possible

Cost of LR6? About $200. Cost of Photos? $0

See the issue?

Or you just unplug the drive from one computer and plug it in to the other. Double click on the Library. No iCloud involved.

baldoyler wrote: I'm not sure what you mean by 'recommended' or what the recommendation is based on. But clearly Photos allows users to have a 'referenced' Library on an external drive (SSD, in my case).

It means that it doesn't work without a great deal of trouble. In spite of the option, a Referenced Library just isn't supported. This User Tip is from several years ago-- we don't run into people purposely using Referenced Files very often:

Disadvantages of a Referenced Library in … - Apple Community

You say, "How does anyone else deal with this ridiculous 'feature'?" but essentially no one else does. A Managed Library works perfectly well on an external Library. I don't really understand why you need the Referenced Library, but Lightroom may work better for you. I use Lightroom Classic as an editor, but not so much as a Library.

Yer_Man wrote: … See the issue?

I think that the issue is that very few people have anything to gain from a Referenced Library, so there would be way more stuff to keep up with for rather little value. Saving the originals inside the Photos Library completely solves the problem of keeping up with them. That, in fact, explains a lot about the nature of the Photos app. I find it remarkable, and while I can add helper apps, I see no need to replace it.