This question is very similar to https://devnet.kentico.com/questions/custom-page-form
However the answer wasn't completely clear in it doest instruct about the UI elements.
The Pages UI is found under Modules -> Content and you can see the particular spot under CMS/Administration/Content management/Pages/Edit, here you see all your items and sub items.
You can create a custom module and add a UI Page here, just tried it out and worked wonderfuly, it's passed the nodeid, culture, and mode in it's url string that you can use to configure.