Hi!
take a look at line 77 of:
https://github.com/qooxdoo/qooxdoo/blob/master/application/mobileshowcase/source/class/mobileshowcase/page/Overview.jsevery time you execute a menuItem in the mobile showcase, you show a page, via the routing configuration in:
https://github.com/qooxdoo/qooxdoo/blob/master/application/mobileshowcase/source/class/mobileshowcase/Application.jsyou can add a route and onGet you can open the dialog with:
when you need to show the dialog you call
qx.core.Init.getApplication().getRouting().executeGet("/mydialog");
This way you end up with a change in the app uri and therefore the history, and the back button will respond as you need.
It's all guessing, I did not tried this by myself.
Could you tell me if that works for you?