The Command Editor is the main route to creating your own buttons, hotkeys, user-defined commands and other functions in Opus. There are several variants of the command editor dialog used throughout the program, although they all have the same basic design.
This screenshot shows two variations of the command editor. The one on the left is the editor for a standard toolbar button - the function being edited is the Viewer Pane command from the default toolbar. The one on the right is the editor for the New Lister hotkey.
If a button's label has an ampersand (&) character before a letter, that letter will be marked as a type of hotkey for that button. When the button is on the top-level of a toolbar, pressing Alt plus that letter activates the button. For example, the File menu's label is actually set to &File - meaning you can press Alt+F to open the File menu. If you want to use a literal ampersand character in the label, you must use a double & instead (e.g. Backup && Restore).
You can also use \t to insert a tab character. This can used in menus to seprate the main label, on the left, from additional information which is aligned to the right. As a convention, it is typically used to display hotkeys. For example, the label for Edit > Paste is &Paste\tCtrl+V to help you know you can use Ctrl+V as a hotkey. Note that the label does not define a hotkey in any way (there's a separate Hotkey field for that), and it's up to you to ensure the actual hotkey is consistent with what the label says it is.
There are two types of hotkeys; local and global. A hotkey you define for a button in a Lister toolbar or menu is a local hotkey, that works only when a Lister is the active window. Global hotkeys work anywhere in the system (as long as Opus is running). By definition, hotkeys defined for buttons in floating toolbars are global. The command editor for a hotkey function (that is, a function that exists solely as a hotkey, rather than a hotkey assigned to a toolbar button) lets you select the local or global state using the System-wide Hotkey option. See the Hotkeys page for more information on defining hotkeys.
If you assign a hotkey to a button that opens a drop-down menu, pressing the hotkey will pop the menu open.
Some of the options in the command editor can be overridden by the settings for the toolbar the button is in - the Show image, Large image size and Show label options can all be overridden by the options in the Images & Labels setting on the Toolbars tab in the Customize dialog.
The Advanced button at the bottom lets you switch from simple to advanced mode.
More:
Simple Command Editor
Advanced Command Editor
Using the Hotkey Control