The "shortcuts" feature found in versions prior 3ds Max 4 has been removed. In it's place you can use macro-recording of actions.
To determine how to invoke an action from MAXScript, you should go to the UI customization dialog and put that action on a button, menu or keyboard shortcut. Then turn on macro recording and execute the action.
The code that is emitted can be cut and pasted in to your script.
If you turn on macro recording and start using the menu, quad menu or toolbar, you'll see code emitted that looks like this
EXAMPLE:
actionMan.executeAction 0 "59225" -- Manipulate Mode
This is code that will execute the same action as pressing the "Manipulate Mode" button. The comment is also generated, and it uses the action's tool tip. The parameters of "actionMan.executeAction" are the integer ActionTableId of the table the action comes from, and the "persistent id" if the action. Actions exported from core all have persistent ids that are fixed integers as a string.
Actions are accessible, all that you need to know are the ActionTableId and the persistent ID in order to invoke the operation.
Certain actions emit much better code. If an action is exported using a function published action table, then the code it emits calls that function. For example, if you bring up the "Plug-in Manager" from the customize menu, the code emitted is: