See T179498 for a general description of what I'm trying to do.

Reproduce the problem

• Go on https://fr.wiktionary.org/wiki/Utilisateur:Psychoslave/accommodation
• edit with VisualEditor, click on the text, the whole stuff is a single template
• wait some time without any clue of what's happening ;)
• tada, here is your TemplateData Widget Editor

Sidenote: I'm currently working on the page, and the underlying template and module, so if it doesn't work, it might be normal. :)

What I would expect

Well, ideally, a pop up with no delay. But if this is not possible, when the UI is loading something, the user should be informed through some visual feedback. Currently there is nothing like that.