Was just wondering if this is working as planned. If you create a new button, and select the COPY command from the function field dropdown, the field is filled with the command CLIPBOARD COPY. I would have thought the command would have just been COPY on its own (if you select the CLIPBOARD command, it inserts just CLIPBOARD into the field).
Not a bug. The simple command editor gives you a menu of action names, not internal command names. "Copy" is an overloaded term, and in this case it's the Edit > Copy command, which puts files into the clipboard.
On the other hand, "Copy File" in the same menu will insert a command like the Copy Files button on the default toolbars.
If you know about internal commands, you probably want to use the advanced mode in all situations. You can turn on Preferences / Miscellaneous / Advanced: button_editor_advanced and the editor will always open in advanced mode, even for single-line commands.