Clarification on leading character removal

I'm trying to follow the example in this post to remove leading characters.

When I create the new action (ALT-F5), I get a dialog "Action Groups". I click on the button for "new". I give it the name "Remove Leading Chars" and click OK. At this point I see a dialog with the title "Actions". It has a blank white box, with OK, Cancel, and Help buttons at the bottom. I cannot type in the blank white box. Clicking Help takes me to the options_format.html page, but it does not show what to do with this dialog. I have attached a snapshot of this Actions dialog.

Edit: I figured it out. At this blank dialog, it is necessary to click the "New" button again, then the action can be entered.