I like it very much so far
What I want to see is a possibility to export to Lite-C and not only to C-Script.
It would also be very interesting to get a preview, but that will probably cause problems with the own functions...
For creating a menu there has to be the posibility to create several "pages" and the possibility to link between them through assigning predefined functions to the panels.
I don´t know, but you could probably allow to create buttons through recreating the panel with pan_create which will make some troubles for the preview but should at least work for the exportet code (within the editor it probably has to be done with panels).
I would prefer ctrl+d for duplicating and the possibility to delete on x as well but thats not really important

I like the overall control and look of your editor and hope that you will finish it because I am really fed with creating such panel stuff