I believe Tobias Beer did something along those lines http://tobibeer.github.io/tb5/#overlay
I couldn't tell you for sure, my system theme makes the overlays hard to differentiate from the underlying page but at tb5 I would often get something like Wikipedia's that would cover the main page's content -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/bbf16153-1749-43d9-9099-652f6216210d%40googlegroups.com.
