Create a new AW.UI.Combo control and put it into the header with setHeaderTemplate(obj, col) method
var combo = new AW.UI.Combo; grid.setHeaderTemplate(combo, 0);
Extended grid allows multiple header rows. Use setHeaderTemplate(obj, col, row) method
grid.setHeaderTemplate(combo1, 0, 1); // first column, second header row grid.setHeaderTemplate(combo2, 1, 1); // second column, second header row
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