Currently, this command switches from Design to HTML mode and vise versa when EditType="Inline".

In Normal editing mode this tool is disabled in the HTML mode and cannot be used, although it is useful and provides yet another layout option for the default look of the RadEditor.

You can test the additional layout option by running this example:

<telerik:RadEditor runat="server" ID="RadEditor1"
    EditModes="Design" OnClientModeChange="OnClientModeChange">
    <Tools>
        <telerik:EditorToolGroup>
            <telerik:EditorTool Name="Bold" />
            <telerik:EditorTool Name="ToggleEditMode" />
        </telerik:EditorToolGroup>
    </Tools>
</telerik:RadEditor>

<script type="text/javascript">
    function OnClientModeChange(sender, args) {
        setTimeout(function () {
            sender.get_toolAdapter().getToolByName("ToggleEditMode").set_enabled(true);
        },0)
    }
</script>

This tool can be redesigned to be available in the HTML mode in all cases not only when Inline editing mode is enabled.