You can use the macOS Finder's Copy command to copy and paste files. But here's how to use the same command to copy file icons into Preview. You've probably used the macOS Finder's popup ...

It turns out that there’s a much simpler—though completely non-obvious—way to get a full set of an application’s icons, at least if you’re running OS X 10.4 or 10.5.

Find the Files app widget and select the plus (+) icon adjacent to it, and then drag the Files app widget to the top of your Today View (using the stacked horizontal line icon). This will allow you to ...

This function can be turned on and off in Finder -> View -> Show View Options by checking the box next to Show Preview Icon, but in some cases it may not work even if you have the setting enabled ...