To be honest, I'm not quite seeing the benefit of this over tapping on the 'share' button in the clipboard toolbar and sharing the selected text with Pleco reader; at most one extra button tap, no need for a hack, and once you've got the text in Pleco, you can look up individual words much more easily than with this system. And with a web page or an email you can just 'share' the whole document with Pleco and not even need to bother highlighting text.
Sharing also feels like much more standard Android behavior, frankly - using popups and notifications in unintended ways may be theoretically doable on Android (unlike on iOS) but that doesn't make it good UX.
Also, we offered a 'clipboard monitor' function in our old version 2.3 (one that absolutely minimized taps - highlight a piece of Chinese text and copy it to the clipboard and Pleco will automatically bring itself to the foreground and provide a definition), but removed it in 2.4 because nobody was using it and it was awkward to get it working correctly on Android 4.0; I believe we received I think a grand total of 1 complaint about that removal, so I'm not inclined to put a lot of engineering effort into bringing similar functionality back again. I'd rather invest that effort into bringing over missing document reader modes from iOS, like EPUB and direct (whole page, not just extracted plaintext) web page viewing.