I am used to right-clicking in Windows Photo viewer to select Copy - something I use all the time to paste a photo into another Window, e.g., WhatsApp Desktop or a file.
Note: recently I discovered that Copy all appears to be the function I need. Why use a different name? Copy all is confusing - I didn't use it before because I thought it would copy all the pictures in the folder
I also tried changing it by editing the rclick menu - but it didn't seem to work.
Sometimes the names of things are slightly different in different software. You quickly get used to it.
"Copy All" is in a group with "Select All" and "Reselect", and the image viewer only displays one file at a time (other than the marked pictures panel, which has its own separate context menu). You can infer from that that it will copy all of the image as bitmap data. If you select part of the image, the label changes to just "Copy", as it will only copy the selected portion. That helps people understand the meaning of the command when nothing is selected.