AEM6.3 contains /libs/cq/gui/components/authoring/dialog/dropdownshowhide/clientlibs/dropdownshowhide/js/dropdownshowhide.js
At lines 49-50 there is this code:
// get the selector to find the target elements. its stored as data-.. attribute
var target = $(element).data("cqDialogDropdownShowhideTarget");
AFAIK data attributes are always lowercase. This is certainly the case if the data attributes are generated via granite:data node as per Common Attributes — Granite UI 1.0 documentation
When I change the code to
var target = $(element).data("cqdialogdropdownshowhidetarget");
my select component works correctly.
Am I missing something?