@Override
			public Dimension getPreferredSize() {
				Dimension size = super.getPreferredSize();
				// change the preferred size to use the width determined by the # of columns in
				// combo box editor instead of the largest item in the combo box data model to
				// prevent the dialog from growing huge when a large label gets added to its recent
				// items
				Dimension editorSize = getEditor().getEditorComponent().getPreferredSize();
				size.width = editorSize.width;
				return size;
			}
Define the Main panel for the dialog here.
Ghidra/Features/Base/src/main/java/ghidra/app/util/AddEditDialog.java