In the GN4 version 2.4 or newer, the designer AddIn commands are available from the Menus and Toolbars even when the designer is open but doesn't have the focus.

The associated keyboard short-cut must must have its IsGlobal attribute set, e.g.:

    <Menuset Name="TxtDesigner">

      <InputConfig>

        ...

        <!--S-->

        <KeyBinding CommandType="Script" CommandParameter="DataSave" 

         Modifiers="Ctrl" Key="S" IsGlobal="true"/>

The above ensures that Ctrl+S is available from places other than with the text designer.