Excellent work! There are so many features I prefer over Koda! 
- I like the control states to be shown as constants 
- I like the way to add styles, By the way, in Koda, you cannot set the constant $BS_ICON on a button without adding a picture, and here it's possible.  
- So easy to copy paste the code 
- Resizing icons are so intuitive 
 
Features I think should be added: 
- Auto declare Global / Local variables. Either like this: 
 Global $hGUI = GUICreate( "New Window", 410, 292, -1, -1)
Global $Button1 = GUICtrlCreateButton( "Button", 140, 220, 100, 30)
Global $Edit2 = GUICtrlCreateEdit( "Edit", 90, 30, 220, 180)
or in one line : 
 Global $hGUI, $Button1, $Edit2
$hGUI = GUICreate( "New Window", 410, 292, -1, -1)
$Button1 = GUICtrlCreateButton( "Button", 140, 220, 100, 30)
$Edit2 = GUICtrlCreateEdit( "Edit", 90, 30, 220, 180)
- maybe a slider to change the transparency of the the grid 
- under the button "Copy script" and "save script", you could maybe add buttons like: "copy constants", "copy Controls", in order to copy without the while / wend. 
- missing an input on the GUI to set the parent GUI (8th param of GuiCreate). 
- If I create 2 tabs, using the button to create a tab, I have 2 Tab items. Then after it's difficult or impossible to delete them. Also sometimes, If I manage to delete one tab and then the other, One tab stays written in the code. 
 
Thanks