ComboBox is below the toolbar, either position it lower or place the GuiCtrlCreateCombo above the toolbar for example:
#include <ComboConstants.au3>
Global $g_hMainGui = GUICreate("Text Editor", $WIDTH, $HEIGHT, -1, -1, $WS_OVERLAPPEDWINDOW + $WS_VISIBLE)
Global $g_idFontNames = GUICtrlCreateCombo("", $WIDTH - 170, 10, 160, 20, Bitor($CBS_SORT,$CBS_DROPDOWN,$CBS_AUTOHSCROLL,$WS_VSCROLL))
GUICtrlSetData($g_idFontNames, _RegEnumVal($FONTKEY));ALSOHERE
Global $g_idFontSizes = GUICtrlCreateCombo("", $WIDTH - 200, 10, 20, 20, Bitor($CBS_SORT,$CBS_DROPDOWN,$CBS_AUTOHSCROLL,$WS_VSCROLL))
Global $g_hToolBar = _GUICtrlToolbar_Create($g_hMainGui)
...