Hi Old Toad,
That's not working here… either with or without the option/alt key, I cannot drag a photo to another app, or Dock icon as has always been possible in the past.
In fact, I can't even do this to Apple Mail or other Apple standard apps, as has previously always been the case in OSX. This is a major loss of functionality. Nothing will drag out of Photos. One used to see a small green dot with a + when dragging out a file. This seems to no longer work in High Sierra. It is making normal working on a Mac a whole set of peculiar workarounds.
his was a major Finder feature built in all the way from System 6. There is no longer a sensibly workable, or universal file moving method in Mac OS.
I have tried a few Photo Library apps in trial mode. I tried Unbound, but this has no export function at all, not even dragging. Lyn has this (what used to be) standard functionality. One can drag to photos to whatever app can accept image files, no problem.
I think I'm ditching Photos. It just seems so rough and unfinished compared with other photo library managers. The inability to copy out my own photos, as well as the inability to view filenames easily. It's clear the designers didn't really know what (or why) they were doing when designing it. It is a desperate disappointment. I slightly regret the update to High Sierra and the loss of iPhoto, a greatly superior (for all its own caveats) app.