I have developed a method of defining the GUI in a spreadsheet and then having Perl that interprets the spreadsheet to create the GUI.
I have used this for the past 6+ years and it works well. In does use the ‘table’ geometry manager which fits in well with a definition based on a spreadsheet table.
The plus points are that I find it very simple to copy and paste elements from one system to another and it is easy to add more GUI widget types. One minus is that the GUIs produced do tend to look similar.