Ed,
I've also figured out that, when not in image "Preview Mode", the "Image | Metadata (IPTC) Template" option shows me the current contents of the global metadata template.
That same menu item also brings up the Metadata (IPTC) Template from the contact sheet. The menu item does not change behavior when a contact sheet window is the active window.
My confusion is the following:
Is there a way to access the "local-to-the-image" metadata info window directly from a selected or right-clicked image in a contact sheet without having "Preview" the image first?
You can get the same Metadata (IPTC) Info window by clicking on the 'i' button that appears when you mouse-over a thumbnail in the contact sheet.
Using the two different metadata windows ("global template" and "local-to-the-image" info window) has been a bit confusing for me as a newcomer. I agree with the layouts being similar for the two windows: you get the consistent familiarity with where to find the same fields across the two interfaces. However, they are so similar, that sometimes it's not immediately obvious which one does what until using the interface for a bit.
I can see how it could be confusing. But there are multiple differences:
1) They have different window titles.
2) They have different layouts (single column in the Info, double column in the Template)
3) Only the Info window shows a large thumbnail of the image. The Template window has no image.
For example, even after reading the docs and forums for a bit I still found myself wanting to use the "Edit Metadata Template" option while viewing a contact sheet to view and edit the metadata for either the currently selected image, or a right-clicked image. It's taken me a bit of use to condition myself that I have to "preview" an image in order to edit it's metadata, and I find that it would be faster sometimes– depending on what kind of work I'm doing – to be able to use the image's metadata window directly from a contact sheet. Perhaps via keystrokes, right-clicking, or as an option in the Image menu.
Use the 'i' button.
Also, using the metadata that's in a recently-taken snapshot has been confusing to me. For a while, I looked for a way to "paste" a metadata snapshot from an image into what I now realize is the global metadata template, but could not find one. Is there a way to do that?
No, not from a 'copy'. But you can bring up the Metadata (IPTC) Info for an image hold down the "Modifier Key" (Option on macOS, Shift on Windows) and click on the "Copy to Template" button.
But is that what the "Copy" and "Paste" buttons on the Metadata Info window also do – copy the metadata to a snapshot or paste metadata from a snapshot? – or just copy the metadata from the current image to a/the "clipboard" for subsequent pasting or paste the metadata most-recently-copied from a/the clipboard?
They're two separate mechanisms. They do not interact or share data.
]Is there a one-click way to access the metadata info window from an image while viewing a contact sheet?
Yes, use the 'i' button as described above.
And is there also a one-click(ish) way to paste that metadata over the current global metadata template, and then save the newly created template as a metadata template setting snapshot?
No one click way to do all of that. You would use the Metadata Info, modifier-click "Copy to Template", exit the Metadata Info window, open the Metadata Template window and then you can make a snapshot by clicking on the Lightning bolt button and giving your snapshot a name. Later you can bring up your named snapshot by finding it in the popup menu when you click the Lightning bolt button (the snapshot button).
And also, is there a way to take a metadata snapshot from an image, and then edit that snapshot directly, say by right-clicking an image and selecting Metadata Snapshot | Edit Snapshot? Or through the Edit menu?
No. But you can edit the Metadata Info before you do the "Take".
Furthermore in the preview window, I find myself many times wanting to right-click images in the "filmstrip", but can't seem to do it. Is that a deliberate design decision, a feature that hasn't been requested and implemented yet, or something else entirely?
There are no right-click options in the thumbstrip and it is intentional.
-Kirk
P.S. If you wouldn't mind, can I ask you to not use the 'list' features in your posts, please? It makes it much harder for me to reply to your questions. I have to edit the quoted post so much that it gets discouraging to do so. I think it more than doubles the time needed to answer your post.