main : dialog {
key = "title";
// ...
}
Not sure what the OP has in mind, but if he wants to change the Label that is the title
of a dialog box, he must generate the dcl on the fly.
The method proposed by ur-naz changes the key value of tile named "Title",
the label that appears at top of dcl will not be changed.
MyDialog : dialog {
fixed_height = false;
fixed_width = false;
...
...
}