How to remap right Control key to Command/apple key

The beeping you are hearing in this context is not because those key commands are mapped to something but quite the contrary because they are not.

Typing an unmapped key command will result in an audible bell.

As you note Command-Control-Right in results in an audible bell in Mail.app. You will also note that Command-N results in a new message.

So here's a proof to confirm my assertion:

• Open System Preferences > Keyboard
• Select Keyboard Shortcuts from the pillbox at the top
• From the menu at the right choose Application Shortcuts
• Click the small + sign at the bottom left of the right panel
• From the Application pull down select Mail
• In the Menu Title field type "New Message" (no quotes)
• Place your cursor in the Keyboard Shortcut field and type Command-Control-Right
• Click Add

Now return to Mail and type Command-Control-Right. A new message will be created but if you type Command-N you will hear the audible bell. This is because Command-N is no longer mapped to anything. We replaced it.

So when you hear the audible bell it often means that you are trying to do something that is not possible (i.e. typing a key command that has no meaning for the current application).

You were looking in the right direction… though you cannot actually do this easily for a right click item - so long as there is a menu item in the same app, it's simple.

I've only quickly tested this on Safari & TextEdit - whichever app you use must already have those 2 command options somewhere in their menu structure.

System Prefs > Keyboard > Shortcuts > App Shortcuts

Select All Applications, then click the + button.

So long as you add the full, correct menu title [& that item exists in the app you are going to be using], the shortcut you ask it to use in the 3rd line will always find it. You don't need to enter any kind of menu hierarchy at all.