Would be quite a welcome addition to DNN wouldn't it?

Well, here's some code I created that solves this but be mindful that this searches by the Name of the Page ... so if you have a root page called Test and put a page who has Test as it's parent and name Level 2, when you search for this subpage it's named ...Level 2 and not Level 2.  Just like Pages look in the Pages listbox.

Public Function GetTabID(ByVal PageName As String) As Integer

        ' Locals

        Dim objTab As DotNetNuke.Entities.Tabs.TabInfo
        Dim arrPortalTabs As ArrayList

        ' Get the Tabs

        arrPortalTabs = GetPortalTabs(PortalSettings.DesktopTabs, False, True, False, True)

        ' Find the TabID based on the Name

        For Each objTab In arrPortalTabs
            If objTab.TabName = PageName Then
                Return objTab.TabID
            End If
        Next

        ' Return

        Return 0

    End Function